Acacia ants, in the genus Pseudomyrmex, and their acacia tree hosts, are a terrific example of coevolution between plants and insects. While yellow flowers and many species demonstrate a loose form of the coevolution between generalized pollinators and a large range of plants, the coevolution in this case is very specific, although there are other examples of Acacias with ants that have a looser association.

The species depicted here are likely Acacia cornigera and Pseudomyrmex ferruginea, native to Mexico and Central America. These photos were taken at Palo Verde National Park in Costa Rica.

While some instances of coevolution may be hard to demonstrate for certain, this case is definitive. First, a common name of this acacia species, bullhorn acacia, refers to the extremely large, swollen thorns shown here. The horns also happen to be hollow, and provide perfect chambers for nesting ants. (An ant on the left thorn can be seen entering a hole in it.)

Next, the tree provides food for the ants in two forms. The first is nectar, but this is not the generalized nectar production of flowers attracting pollinators. The acacia nectar is provided from extrafloral nectaries, found actually on the leaf petioles, as shown here (slightly out of focus). Because of the location and size of these nectaries, it is clear that the trees are obtaining a benefit apart from pollination.

Second, the tree also produces a unique protein source for the ants called Beltian bodies (after the naturalist Thomas Belt). These extraordinary structures are produced as part of new developing leaves. When the new leaves unfold and expand, there is a Beltian body on the tip of each leaflet. These are harvested by the acacia ants and provide most of their protein. Between the nectar and the Beltian bodies, and the housing provided by the thorns, the tree provides all an ant colony's needs.

What does the tree get in return? It gets extremely aggressive defense from herbivores, both large and small. Pseudomyrmex have one of the nastier stings in the world of Hymenoptera (the order comprising ants, bees and wasps). Any insect that alights on the tree is instantly driven away or killed, and the ants are quite effective against potential vertebrate herbivores as well -- to which I can attest first hand when I made the mistake of brushing against a branch while taking these pictures.

The ants are so aggressive that they also take care of potential plant competitors, by cutting down any seedlings that sprout in the vicinity of the tree. In this photo it should be clear that the acacia in the center is sitting in a circle of bare dirt, courtesy of its ant colony.

The relationship between the acacia tree and Pseudomyrmex ants is thus a true mutualism, in which both species have a large benefit from the association.

Labels: cool bugs, ecology, evolution, insects

Is mathematics an emergent property of sociality? I posed this intriguing question to a mathematician colleague, who is also an evolutionary biologist, and he said yes. The question came up because I have argued that rules are actually a social construct; a solitary species needs few or no rules governing its interactions with other individuals of its species, because other than mating or occasional territorial conflict, it has almost none. Individuals in social species, by contrast, are completely dependent on rules to survive and reproduce, because interactions with other members of the species are constant, and determine standing within a social group, and thus generally reproductive success.

Most evolutionary arguments applied to humans are tenuous, because of cultural complexities that overly our basic biology. Complicating the picture further, aberrant behavior (that which does not comply to a given social norm) is also probably more common among humans than among other social animals, because 1) we have chemical treatments that suppress some symptoms of such conditions, 2) we have easy access to addictive products which our brains did not evolve to cope with, such as drugs, junk food, slot machines, etc., and use of these can lead to self-destructive behavior, and 3) many aberrant people are smart enough to overcome or disguise their problems enough to fit in somewhat. So, there are many ways in which humans seem to get away with behaving in socially maladaptive ways, without suffering reproductive consequences, as other social primates probably would.

However, we did evolve as a social species, and much of our behavior is indeed a legacy of that evolutionary history. The playing of games is an example. Games are all about rules. Kids love learning new games, because their brains are wired to learn rules -- particularly rules for navigating in real society, but an artificial society with artificial rules will do. Whether it is sports or war games or pin-the-tail-on-the-donkey, humans love games. Games with complex rules are more fun to learn for many of us, but those with fairly simple rules but complex strategy, such as Go or hearts or chess, usually capture the most active minds. It is our love of rules that make us despise the referee who makes a bad call. In our minds, if a rule is broken, the entire game should be void.

It seems that mathematics is universal, a truth that existed before humans and that they discovered. But to humans at least, mathematics is also all about rules, and perhaps the way that we perceive mathematics is filtered through our obsession with rules. We all learned them at the beginning of every school year for a decade. "Addition and multiplication are commutative. The transitive property says that if a=b and b=c, then a=c. The distributive property says that a * (b + c) = a * b + a * c" and so on. If you take higher level math classes in college, you discover that there are other mathematical systems with different rules; for instance, matrix multiplication is not commutative. So math is indeed a world of many rules that apply one way in one context but another way in a different context, very much like the rules of social interactions -- for example, it is inappropriate to wear a bikini at the opera, but just fine at the beach.

Although many would protest the truth of the statement, humans are wired for math. (If you hate math, it is not that you are "no good" at it; it is because the way it was taught to you made it painful and boring. This is a persistent problem that will likely never be corrected on a large scale, because of the vicious cycle of elementary school teachers who dislike math and barely get through it in college, go on to teach it poorly, cause their students to dislike it, and so on.) The interesting question is, would, or could, an intelligent solitary species have developed math? Some would say the question is completely moot because only a social species would have evolved brains as large as ours, because sociality requires a larger brain to navigate the intricacies of social interactions, in addition to the basic needs of finding food and mates and defending oneself. It is perhaps a chicken-and-egg question. But what is no question is that complex rules govern sociality, human brains are therefore wired to learn and use rules, and mathematics is a system of rules. Mathematics, very much like religion, is likely a byproduct of our success as a social species.

Labels: brain, evolution, humans, mathematics, sociality

The Belostomatidae is a family of giant water bugs (Order Hemiptera) that has been fairly extensively studied because of the various species' unusual reproductive systems. In short, this is one of the few groups of animals that exhibit paternal care of offspring.


Probably the most well known animals with paternal care is the sea horse, who carries its mate's eggs in a brood pouch until they hatch. Belostomatids are similar because the male also takes care of the eggs, although he does it in two different ways between the two subfamilies, Lethocerinae and Belostomatinae. Above is a giant water bug in the genus Lethocerus. They are sit-and-wait aquatic predators, hanging head down on sticks or reeds underwater. An appendage extending from their abdomens remains above water and allows them to breathe. They are quite large, and much of their prey consists of tadpoles and small fish.


They have a somewhat painful bite, because they have a sharp beak with which they inject a neurotoxin which helps them control their prey. However, if one holds them just behind the head as shown it is safe to pick them up. (I was holding this particular specimen (from Costa Rica) that another student and I were studying; we were doing measurements to look for morphometric differences between males and females, and I had to do all the measuring because he was too afraid to pick one up.)

The Lethocerines are thought to be the more ancestral lineage in the family, based partly on the way they brood their young. Females lay eggs along the top of a stem sticking out of the water, but the eggs will dry out and die without care. The male stays as a sentry on that stem, periodically carrying water up to moisten the eggs and oxygenate them.


The Belostomatines are considered more derived evolutionarily, because the brooding behavior seems to be more efficient. Females lay their eggs directly on the back of the male, who must swim around with them until they hatch to keep them properly oxygenated. The picture at left shows a male with eggs.

Scientists like to study "reverse mating-system" species such as these because it gives us clues about what governs decision-making in animals. In the case of mating behavior, in nearly all animals known, females are choosy about their male mates, who often have elaborate physical features or behavior designed to attract the attention of females (or fight off other males). This is why in many species of birds, the males are more brightly colored than the females. The reverse mating-system species allow us to ask questions like, are females always the choosy ones, because they invest more resources in their gametes (eggs are a lot bigger and fewer than sperm), or is the parent with the largest investment overall the choosy one? Gamete size is an important measure of investment, but time and energy invested in a single mate are important too. In most animal species, a male has the sperm and the time to mate with many females, so he tends not to be choosy. A female not only has fewer gametes but usually invests more time in rearing the offspring than the male, so it's more important that she choose a mate with good qualities (for that species).

It has been found that in reverse mating-system species, the males actually tend to be the choosy ones - so there's nothing about being female per se that makes one choosy. Parental care of offspring is a huge investment, so when it switches to the males, they become the choosy ones. In the case of giant water bugs, a female may have enough eggs to mate with several males, and as soon as she lays them she can move on and find another mate. The male is the parent stuck taking care of the eggs for a couple weeks and thus loses opportunities for more matings in that time. Thus, accordingly, belostomatids and sea horses tend to have choosy males rather than females.

Labels: cool bugs, ecology, evolution, insects, sex

Almost as a reiteration to my earlier post, here is another article close on the heels of the last, about drying conditions in the West. Climate change is not a vague, unproven myth that wacko lefties perpetuate in order to undermine Big Business. It's here, folks, and because it is being combined with other fast-acting anthropogenic effects (that I previously discussed), ways of life and species assemblages in the West will be radically changing in the next couple of decades.

And, having done ecological research (my dissertation) in high altitude zones of the "sky islands" myself, on species that may cease to exist in the southern half of Arizona within my lifetime, it is not exactly with glee that I draw your attention.

Labels: biodiversity, ecology, environment, evolution, invasive species

Frans de Waal is my new hero. He has performed a body of research on various non-human primates which has demonstrated that at least a minimal level, morality is a byproduct of sociality, rather than a unique human construct. His experiments are well designed, and essentially make it clear that the "golden rule" morality of "do unto others as you would have them do unto you" is an important system that helps hold many primate groups together.

As he writes in an essay from the New Scientist ("The animal roots of human morality," October 14, 2006, pp. 60-61):

In The Descent of Man [Darwin] wrote: "Any animal whatever, endowed with well-marked social instincts... would inevitably acquire a moral sense or conscience, as soon as its intellectual powers had become as well developed, or nearly as well developed, as in man."

It is not hard to recognise the two pillars of human morality in the behaviour of other animals. These pillars are elegantly summed up in the golden rule that transcends the world's cultures and religions: "Do unto others as you would have them do unto you." This unites empathy (attention to another's feelings) with reciprocity (if others follow the same rule, you too will be treated well). Human morality as we know it is unthinkable without empathy and reciprocity.

It has always been strange and interesting to me (as de Waal makes it clear it is interesting to him as well) that this basic rule does not seem to be recognized by a lot of people as the cornerstone to human morality. I believe it is embraced by secular humanists, but in many cultures, religion has interfered with and been confused with human morality, when in fact morality predates religion and in fact has nothing to do with religion. Religious morality is actually a set of rules to distinguish the practitioners of certain religions from the rest of the world, the "outsiders:"

Our evolutionary background makes it hard to identify with outsiders. We've been designed to hate our enemies, to ignore people we barely know, and to distrust anybody who doesn't look like us. Even if we are largely cooperative within our communities, we become almost a different animal in our treatment of strangers.

Also:
Empathy is the one weapon in the human repertoire able to rid us of the curse of xenophobia. It is fragile, though. In our close relatives it is switched on by events within their community, such as a youngster in distress, but it is just as easily switched off with regards to outsiders...
(de Waal, "The empathic ape," New Scientist October 8, 2005 p. 52)

This relates to a previous post of mine on the tendency for humans to "switch off" their empathy when communicating over the internet, either to a specific individual through email, or via the blogging culture of mass demonization of a defined group or individuals supposedly representing that group.

It also turns out that the effort to conform in order to fit into society is not limited to humans, either. In a Nature article (Andrew Whiten, Victoria Horner & Frans B. M. de Waal, 2005. Conformity to cultural norms of tool use in chimpanzees.
Nature 437:737-740), de Waal and colleagues found that when two chimpanzees, from two different social groups, were each taught a different way of working the same machine to receive food, chimps not only learned the method taught the chimp from their group, but preferred it even when they figured out the other way too. From the abstract:

... A subset of chimpanzees that discovered the alternative method nevertheless went on to match the predominant approach of their companions, showing a conformity bias that is regarded as a hallmark of human culture.

The conclusion of that article states their experimental results plainly:

...[W]e found evidence of a conformist bias, identified in numerous human studies as a powerful tendency to discount personal experience in favour of adopting perceived community norms...

These results suggest an ancient origin for the conformist cultural propensities so evident in humans.

Here's one more interesting paper, which found that primates participating in games designed to see if animals will always act in their self-interest, often did not. This is a well known idea about humans in economic circles. For example, there is a game in which two people have to agree to accept a certain amount of money. If one person does not agree, neither gets the money, but if they both agree, they both do. If two people are given the same amount of money, each happily takes the reward. But although it is always to a person's benefit to accept any amount of money, most people will reject the money if they find out that the other person would get significantly more than they do. This result probably is not too surprising to most of us.

It is interesting, though, that de Waal and his colleagues have found a quite similar behavior in primates (Sarah F. Brosnana,and Frans B. M. de Waal, 2005. Across-species perspective on the selfishness axiom. BEHAVIORAL AND BRAIN SCIENCES 28:818):

We know that some nonhuman primates react to being relatively underbenefitted compared to a conspecific, which is irrational according to a strict self-interest paradigm.

I find myself disagreeing with the statement that this behavior is irrational, however. In the context of sociality, it is not, necessarily. The basis of sociality is reciprocity, and therefore it makes sense that even animals behave as if there has been an injustice in this case. I think a functional society needs to demonstrate that there is a minimum of justice. Those human societies in which this minimum is not met are not productive, or functional, in my opinion.


And based on experiments to look at the idea of sharing, another social behavior, in primates, these same authors state:

...there was virtually no sharing between the privileged individual and their less well-endowed partner...It is interesting, therefore, that the relatively benefited individuals did not exert more effort to equalize rewards.

Interesting, perhaps... but certainly consistent with human behavior as well.


Based on this extensive research on non-human primates, the origins of both conformity and morality are clearly pre-human. Each is a double-edged sword - the dangers of groupthink (especially within a "social group" of leadership) should be clear to everyone, and the "golden rule" can create problems when people across cultures (an everyday occurrence in today's world) are attempting to interact - treating someone the way you would want to be treated results in people taking offense all the time.

Humans love to believe we transcend biology, because we are not mere "animals." Based on de Waal's work, however, it seems we may be doomed to be limited by the structure of brains adapted to functioning within small societies. Globalization has been far too rapid to even imagine that any evolution to cope with its intricacies has occurred.

Labels: brain, empathy, evolution, morality, sociality

I thought about doing a post on all the wasp mimics out there, but within the flies (Diptera) there are plenty, and it clearly evolved multiple times - in most cases, not all the species within the following family are mimics. Obviously it would be some benefit for any insect to be thought a wasp by a vertebrate predator. Flies cannot sting for defense, so some of them just look a lot like wasps so predators will think they can sting. The ways in which they mimic wasps are fascinating.

The following families include wasp mimics: Micropezidae, Conopidae, Mydidae and Syrphidae. I'm surely missing some - don't be shy about pointing it out, all you Dipterists out there.

There is a whole family of bee mimics as well, the Bombylidae (the bumblebee genus is Bombus). They are big fuzzy things (below right), but if you look closely, you will see only two wings, which gives away their lineage - all bees and wasps (and all orders of insects except for the flies) have four wings.

But I'm more interested in the wasp mimics here. I'll start with my favorite, a Micropezid I caught in Costa Rica, at the La Selva research station. These are fantastic mimics, and a still photo just doesn't do them justice because their behavior is an important part of the package. You can see the fly has a pointy abdomen, which helps, and when grabbed, it pokes its abdomen into the grabber's skin repeatedly as if to sting. (Kinda cute, since it's completely harmless.) The other important combination of morphology and behavior has to do with the long forelegs, which end in white tips (which you should be able to see in the photo, along the edge of my thumbnail). In the tropics especially, the long antennae of stinging wasps have white or yellow tips. Flies, as a group, have very small antennae, but this family of flies has long legs. It was a quicker evolutionary step for the mimic species to use its forelegs to mimic antennae, than to develop long antennae itself. So you will see this fly walking rapidly along leaves in the manner of wasps, tapping its forelegs in front of it just as wasps use their antennae. It's really amazing to watch. (Although this fly family is more ubiquitous in the tropics, there are North American species and I have seen them in central Virginia.)

Conopids have a generally different look, mimicking thread-waisted wasps (Sphecidae) rather specifically. A common wasp-mimic morphology is to have a somewhat constricted abdomen, because a distinguishing character of the Hymenoptera (ants, bees, wasps) is a distinct constriction in the first few abdomenal segments, which means that hymenopterans are more or less restricted to liquefied foods, but also allows flexible reach for the abdomen when stinging prey or for defense. The conopids combine this with the elongated abdomen characteristic of sphecid (digger) wasps. I'm not aware of any specific behaviors that help promote their ruse.

Some Mydidae (mydas flies) apparently go for the pompilid (spider wasp) look. According to the source for this photo of Mydas clavatus, Tom Murray, it is mimicking spider wasps in a particular genus, Anoplius. Pompilids have a quite characteristic look of a black body and darkly pigmented wings. The photo on the right is Anoplius.

The syrphids (hoverflies) are not so precise in their mimicry. Here are two, with one clearly mimicking a bumble bee, and the other just looking generally wasp-like with its black and yellow markings. Their behavior does not necessarily contribute to the show; as their common name suggests, syrphids spend a lot of time hovering, which is generally unwasplike.








Thus mimicry takes many forms. It is interesting that some mimics seem to be modeling specific insects while others just seem to have the general look of wasps or bees. Does the selection pressure differ for these mimics, and why? Perhaps the generalist mimics live where there are a big enough variety of stinging Hymenoptera that they don't need to get specific. Why do some converge on specific families? Is there a dominant model present in those habitats? I'll admit up front that I have not done a literature search, so I don't know what is known specifically about the evolution of mimicry in these groups. I just like them because they are so cool.

The only picture of mine above is the worst one by far, of the micropezid. The syrphids and Anoplius come from Forestry Images, a wonderful image database, and the rest are by Tom Murray, and used with his permission. See many wonderful fly images of his here.

Labels: bees, biodiversity, cool bugs, ecology, evolution, flies, insects, wasps

Pharyngula has already had an excellent post and subsequent discussion about last week's Times magazine article, "Darwin's God." Of course that's not going to keep me from my own pontification. I agree wholeheartedly with PZ on most points, but I hope to add to the discussion by commenting on what I thought were the more irritating quotes from the article.

The spandrels vs. adaptation dichotomy irritates me. An evolutionary spandrel may become adaptive in a context different from why it appeared. But the biggest problem with the whole article is the discussion of human evolutionary adaptation. Such discussions seem to be getting more and more popular, but are just a sign that our society today has swung way back to the "nature" explanations from the "nurture" explanations that were prevalent in previous decades. They are not any more valid today than they were a hundred years ago, but people actually have this idea that scientists have figured all this stuff out, just because we know how to sequence a gene now. Culture is completely intertwined with ecology for humans, and yet everyone wants to make ecological arguments for why we do things. It makes no sense. Culture is so plastic that anything said about evolutionary pressures hominids faced a million years ago is a made up just-so story. Evolutionary psychology is bogus, because it's just too easy to make up any story about humans' past that fits your pet theory.

Maybe cognitive effort was precisely the point. Maybe it took less mental work than Atran realized to hold belief in God in one's mind. Maybe, in fact, belief was the default position for the human mind, something that took no cognitive effort at all.

Although at first reading this seems an outrageous statement to a true atheist, I think on one level it has validity - I just argue with its assumptions about why some people apparently find it easier to believe in a god than not. The number one reason is culture: most of us have been brought up to believe in a god, so that does indeed become the default position for the majority out there who aren't that interested in thinking the idea through. For most, following the culture we are born into is not only simpler, but probably more adaptive as well (in terms of reproduction). But what that means is different for every place and time in human history.

Folkpsychology, as Atran and his colleagues see it, is essential to getting along in the contemporary world, just as it has been since prehistoric times. It allows us to anticipate the actions of others and to lead others to believe what we want them to believe; it is at the heart of everything from marriage to office politics to poker. People without this trait, like those with severe autism, are impaired, unable to imagine themselves in other people's heads.

This is an important point (touching on the importance of human sociality without spelling it out as such), and relates back to a previous post of mine.

They had learned that, in certain situations, people could be fooled -- but they had also learned that there is no fooling God.

The bottom line, according to byproduct theorists, is that children are born with a tendency to believe in omniscience, invisible minds, immaterial souls...

OK, this was commented on at Pharyngula, but I just have to add my agreement that this is one of the stupidest things anyone could say, and illustrates that the author of the article doesn't understand atheism at all. It also relates to something I have pointed out previously, that just because young children do something doesn't make it genetic. It's mind-boggling they could go from the previous statement about how important sociality is, to this statement which assumes babies live in some sort of vacuum and learn nothing about the society around them. And yet everyone knows and comments on the silly things toddlers do in imitation of adults and other kids. Belief in Santa Claus, the Easter bunny, and God is learned.

"Our psychological architecture makes us think in particular ways," says Bering, now at Queens University in Belfast, Northern Ireland. "In this study, it seems, the reason afterlife beliefs are so prevalent is that underlying them is our inability to simulate our nonexistence."

I like this analysis of why afterlife belief is so prevalent. For each of us, the universe only exists as filtered through our bodily senses. There is no objective reality. So we cannot imagine a reality that does not involve the use of our senses. Because it is impossible to imagine it, our brains hurt less to assume it doesn't exist.

...religion filled people with "a new zest which adds itself like a gift to life . . . an assurance of safety and a temper of peace and, in relation to others, a preponderance of loving affections."

It is just as easy to argue that the negative elements of religion would be destructive. Picking and choosing the "positive" aspects of religion is ridiculous, as Mark Twain pointed out in satirical essays about people who attribute all good to God, but do not blame God for all the horrible disasters in life (which in the life of the average person on this planet, arguably way outnumber the good things).

...helped them attract better mates because of their reputations for morality, obedience and sober living.

Even if you argue that these are all components of successful religions, this is bogus because in most people's cases, this is only the facade and not how they actually live their lives. Was it more genuine in the past? No way to know. But clearly for the major religions today, there are too many cheaters in the system to make membership in a religion a reliable signal for a good mate. There is a literature on ecological relationships that shows the mathematical level at which a mutualism breaks down because the number of cheaters makes it nonadaptive to trust your partner - this selects against the cheaters, presumably, and in many nonhuman mutualisms, a balance is achieved through selection. But when it comes to humans, culture is once again complicating the issue. It is nonadaptive for beaten women to return to their mates over and over again, but domestic violence is often sadly a cultural norm. To an abused woman, there are usually other perceived social repercussions in defying that norm, not to mention the perception that they would be worse off without the beater. So nonadaptive behaviors on the individual level persist in humans (various other addictions are another example), due to cultural reasons that cannot be ignored when one is making 'evolutionary' arguments.

"Religious and secular rituals can both promote cooperation," Sosis wrote in American Scientist in 2004. But religious rituals "generate greater belief and commitment" because they depend on belief rather than on proof. The rituals are "beyond the possibility of examination," he wrote, and a commitment to them is therefore emotional rather than logical -- a commitment that is, in Sosis's view, deeper and more long-lasting.

Unlike PZ, I think I agree with this. There is more to being in some thing perceived as a religion than being a Trekkie. Yes, people love to form clubs, and that is an outgrowth of our sociality. But religion works best for forming groups because:

1) Most people hate to think - any teacher or professor knows this - because it takes more energy than not thinking. Religions are convenient for nonthinkers because since they involve non-factual matters of faith, there is always someone telling you how to think, so it is easy to be a member.

2) Religion also combines the group-forming with the comfort of someone telling you that your crappy little life has some larger meaning. It also tells you that you will live forever, which appeals to everyone's fear of death (which is completely natural - heck, yeah, I fear death, so I try not to think about it!). You are also being told in most successful religions that personal responsibility is not important. Either whatever happens to you is the fault of infidels, or you will be forgiven as long as you confess, etc. Man, how appealing is that?

3) Religion is much better in fostering the us vs. them dichotomy that humans again tend to by virture of sociality. Like ants, we have a need to recognize "nestmate" from "nonnestmate," because we are competing for resources with the "nonnestmates." Civil War reenactors don't have any particular adversary that bonds them as a group (except maybe all the non-Civil War reenactors who think they're nuts). Costumes, behavior, etc. all are useful many societies to recognize whether or not someone believes in your god or the wrong one.


In sum, I completely agree with others who found the idea that it is difficult to "resist" religion completely bogus. I, like PZ and others, feel no such tendencies whatsoever. Again it is clear the author doesn't truly understand what atheism is. For me, it is not only being a 'non-believer.' Much more important, it is being competely comfortable with a universe in which there is no God and in which where we are today was arrived at solely by chance. My worldview is as natural to me as the worldview of some one who claims to be 'religious.' Don't you dare patronize me by saying that it isn't, because it's just as easy for me to think you are the misguided nut as vice versa. I prefer live and let live, which means: don't try to convert me, and don't make laws affecting me that are based on your religion.

What is the true difference between natural atheists and natural theists? In my view, it is the desire to think deeply about the world at all levels, without having to believe that in the end my life has to have some sort of meaning that ties neatly into the natural world. My thought is the emergent sum of a lot of complex (to me) chemical and electrical processes. Death is the end of those processes, period. I used to wonder why open atheists were in the minority. (No matter what the polls say, I am skeptical that there are as few atheists as people believe.) Now I understand that the 'deep thinkers' that identify themselves as theists just need that crutch; they need to think that their life somehow has meaning within the vast unknowable universe. This seems a natural state for a social species - the need to be accepted by society could easily be projected onto a god as well, once the species achieves awareness that there is a lot more out there beyond their patch of forest. After all, your own personal god will never desert you, will always forgive you, etc. Those of us who don't feel the need to be accepted by a god may have less of a need to be accepted by society as well (although we tend to find our own godless societies to be a part of). We probably have transcended biology at some level, because knowledge has set us free.

Labels: evolution, humans, religion, sociality

What do you think this sound is? Continue reading for the answer...

Since it's been two weeks since my last "cool bug" post, I thought I had better change the name of the series... we'll see where it goes from here.

Today's subject is a fruit fly, Rhagoletis juglandis. This is not related to the fruit fly of genetics fame, Drosophila melanogaster, which is in a different family. Nearly all drosophilids only eat fruit once it is rotting; flies in the family Tephritidae, including the genus Rhagoletis, feed on ripe fruit and thus are known to entomologists as the "true" fruit flies.



I will admit up front that these flies are mainly of interest to me as larvae (at the left), because they serve as hosts for one of my favorite parasitic wasps, Diachasmimorpha juglandis, below. R. juglandis larvae feed on and live in the fruit of the Arizona walnut (Julglans major) (i.e., the husk surrounding the actual nut), and D. juglandis females parasitize them through the walnut fruit skin.


The fly larvae live in groups in the walnut husk, sometimes by the dozens. All the larvae in a fruit may or may not have the same parents, if there have been multiple ovipositions in the fruit.




In the picture to the right is a mating pair of R. juglandis adults on a plastic walnut model. Males and females mate multiply, with several individuals if given the opportunity.





There are territorial contests by the males on the ripe walnuts while they are still hanging in the tree. This behavior is known as "boxing." The males stand on their hind legs and bat their forelegs and wings together. (In the picture to the left, the wings are only a blur.) The idea is that the winners of these contests have access to more females, who will come to the walnut to mate and lay eggs. Some poor females are forced to mate as they extrude their ovipositors to dig a hole in the husk in which to lay eggs; the males will grab them from behind and mate with them before they have a chance to oviposit. Sometimes, though, males are so intent on fighting with each other that they don't seem to notice a third male that is mating with the female on the fruit while they are going after each other.


While males are duking it out, mated females also get the opportunity to finally oviposit without harassment (left). A female drills a hole in the husk with the tip of her ovipositor (which eventually shows signs of wear) and deposits several eggs in a cavity just beneath the surface of the husk. These grow and feed inside the husk until they are ready to pupate, when they exit the fruit and burrow into the soil. Sometimes there are so many larvae within the husk of a walnut that their feeding is audible. Click here to listen to the sounds of feeding fly larvae in a walnut.

Unfortunately for the larvae, the racket they make chowing down on the walnut is their undoing... as will be revealed in the next Cool Bug of the Fortnight!

Here are references for more information on Rhagoletis juglandis:

Papaj, D.R., 1994. OVIPOSITION SITE GUARDING BY MALE WALNUT FLIES AND ITS POSSIBLE CONSEQUENCES FOR MATING SUCCESS. BEHAVIORAL ECOLOGY AND SOCIOBIOLOGY 34 (3): 187-195.

Henneman, M.L. and Papaj, D.R., 1999. Role of host fruit color in the behavior of Rhagoletis juglandis (Diptera: Tephritidae). Entomologia Experimentalis et Applicata 93:247-256.

Nufio CR, Papaj DR, Alonso-Pimentel H, 2000. Host utilization by the walnut fly, Rhagoletis juglandis (Diptera : Tephritidae). ENVIRONMENTAL ENTOMOLOGY 29 (5): 994-1001.

Labels: biodiversity, cool bugs, ecology, evolution, flies, insects

One of the most species-rich families of plants in Hawai`i is the Rubiaceae, or coffee family. Several of these will be apparent as you walk along the boardwalk in the Alaka`i Swamp. While 22 species of the rubiaceous genus Hedyotis are listed in the Manual of the Flowering Plants of Hawai`i (Wagner et al. 1999, Bishop Museum, Honolulu), one species, Hedyotis terminalis (manono), has dozens of subspecies and varieties listed. The Manual says that this species "is probably the most polymorphic species among Haaiian flowering plants except perhaps Metrosideros polymorpha" [ohi`a, described in Part 1].

You can say that again. As I began my research project, I brought specimens of most of the plants to the botanists at the National Tropical Botanical Garden in Lawa`i for identification. After a few months I had learned the local species well enough, but in the process I believe I brought specimens of H. terminalis to one botanist at least four times. It got to be a bit embarrassing, but eventually I got a feel for the gestalt of this species.

Which brings me back to the end of Part 1, in which I suggested that the word 'species' itself may be inadequate to describe the current state of Hawaiian plants along the evolutionary continuum. The Manual admits there is no easy way to classify either H. terminalis or M. polymorpha into multiple species. Similar problems exist in some insect groups. Those doing DNA analysis of island endemics usually find similar genetic variation within a species to that between related species, which means it is nearly impossible to find genetic markers to distinguish species. Only by doing an analysis of multiple genes and seeing where an individual insect falls out on a plot of other known insects is it possible to identify it genetically. As I did with some plants, I had similar problems recognizing with certainty one moth species, Scotorythra rara, the most common one in the swamp. Once again, with the help from an expert in that genus, I understood the range of variation in that species enough to recognize it on site.

But given these difficulties, how do we know these moths or plants are all in the same species? Morphology is certainly useful, and in many insects, genitalia structure is key for separating species. But is it definitive? I'm not sure. For most Hawaiian insects, some major information is missing - their ecology and behavior. Entomologists in the islands work almost entirely with dead specimens, knowing little about how they live their lives. Among the hundreds of insects I reared and called S. rara, there were not only dozens of food plants, but multiple morphologies of the larvae (which are inchworms). When I first began rearing the insects, I assumed all these would be different species. And no one has a clue about their mating behavior, which is theoretically crucial to the actual definition of a species - if two individuals can interbreed and produce fertile offspring, they are usually (but not always, especially in plants!) considered the same species.

There is another genus of moths that positively exploded in its radiation in Hawai`i, called Hyposmocoma. There are over 300 described species of Hyposmocoma, and many in description limbo. I would not be surprised if there are actually over a thousand (as there are of a more studied fly genus in Hawai`i, Drosophila). Unfortunately, these are tiny moths, and even less is known about their life histories than about Scotorythra. An eminent entomologist I worked with on occasion at the British Museum of Natural History had tried to work on the taxonomy of the group, and had simply given up. Many specimens he studied with similar genitalia had different wing morphology, and vice versa. The larvae are case bearers, meaning they hang out in a little silken bag, and for some species the structure of the case seemed to be distinctive. But for most, it is apparently not.

Why are species so hard to separate in Hawai`i? Evolution is a continuous process, that has no endpoint. But because the Hawaiian Islands are so recent in geological time, and it is so rare for any living thing to arrive there on its own over vast expanses of ocean, I believe we are still witnessing the messy sorting out of niche-filling. The traits of different species drift and become more distinct from each other through several processes, including physical separation (via geological events, for example) and assortative mating (in which more similar individuals mate and reproduce). In Hawai`i, we have to ask, who knows what a species is? because we have not found a way to actually watch how individuals from all of these different groups interact with each other, and the environment. Speciation is not an instantaneous process, and in Hawai`i, along the boardwalk of the Alaka`i Swamp, we are watching it happen.

The plants and insects of the swamp are finding their way. Unfortunately, the evolutionary process can no longer stay on its natural course in Hawai`i, because of the habitat destruction and thousands of alien species that are invading the natural areas like the swamp and creating selection pressures that would not have been there without humans. I feel fortunate to live during the time that I do, that I had a chance to see a glimmer of what Hawai`i was really like. Of course, I don't know an ecologist there who doesn't wish we could go back in time a couple hundred years before Europeans came, or even a couple thousand years before humans were there at all. We have to be content with the few slivers of the real Hawai`i that are left, and do our best to protect them, although the future looks bleak. When I am in the Alaka`i Swamp, I forget about the continuing destruction below me. As I peer through the mist, all I think about is the wonder of evolution.

For more about the moths and plants of the Alaka`i Swamp, click here.

Labels: environment, evolution, Hawaii, invasive species

The Alaka`i Swamp on the island of Kaua`i is not easy to get to. It used to be you could drive any rental car to the head of the Pihea trail and from there be quickly on your way into the swamp, but more often than not now the last mile or so of the road is closed due to potholes and persistent underfunding of the Hawai`i state parks system.

But in any case, the hike in is quicker from the Alaka`i Trail head. The 3-mile drive there, though, is not for the faint of heart these days. I was lucky; I began my research there in 1998, in the midst of a 4-5 year dry spell during which the road had just been graded; this may happen only every decade or so, probably whenever a bit of money can be freed up to do the work. By my last summer in the swamp in 2002, it was wet again, and the choice in many places was between trenching through foot-deep ruts or skating along the slick edges, while gunning the engine to get uphill, and beyond a steep drop-off to the deep canyon below.

From the trail head it is about a half mile until the beginning of the boardwalk. The boardwalk, built around 15 years ago, is a huge boon to hikers and researchers alike, and has helped protect a fragile ecosystem from constant erosion and trampling. The plants along this first part of the trail, including alien eucalyptus, fire trees, and the beginning thickets of strawberry guavas, are likely foreshadowing the future of the swamp; each time you return you notice the aliens have encroached a bit farther in. It's not just plants; it was a shock for me to discover ants in the swamp in 2002, never having before seen them in all the long days I worked there. (There are no native Hawaiian ants, but 40+ alien species have arrived on the islands, mostly via the horticulture trade.)

Finally, as you leave the edge of the boardwalk behind and march deeper into the Alaka`i Swamp, most of the alien plants melt away, and you are transported into a wonderland of island biogeography. Islands tend to have unique native flora and fauna, with many endemic species (occurring nowhere else). The farther the island from a continental land mass, from which species have naturally invaded over the millenia, the fewer the number of common ancestors that the island's species have. In taxonomic terms, this means you can end up with hundreds or even thousands of species within a single genus, as the descendents of a single common ancestor -- the seed washing up from the ocean, blown on the wind or stuck to a bird; the gravid female moth or ballooning spider blown off course for a thousand miles -- diversify rapidly (in geological time) to fill a whole new land of empty ecological niches. At the same time, whole taxonomic families of plants, insects, and birds do not exist in the islands, because serendipity did not bring them here.

This results in the unique jungle you pass through along the boardwalk, with one of the richest native plant assemblages remaining in the islands. The invaders are working their way in, though. To a local ecologist, the tangles of thorny blackberry plants and the sweet August aromas of kahili ginger blooms jar the senses, and turn the stomach. These don't belong here. They come from places distant enough that they could not have arrived by any method other than active human husbandry. But the blackberry is reaching farther and farther from the trails, its thorny branches and leaves standing out. No Hawaiian natives have thorns, including a native blackberry that supposedly occurs in the swamp, but that I have never seen in the wild. No native herbivorous mammals means no need for thorns; the imported pigs and deer here find the native plants quite succulent, and eschew the aliens with their defenses in place.

The ginger starts in a thick clump and spreads from there, quickly dominating light gaps before the slower native plants can gain a foothold. Despite the ecological damage this plant is doing, several species species of ginger are still sold as ornamentals. Apparently the profits of the horticulturists are more precious to Hawai`i's government than an ecosystem being slowly wiped forever off the face of the earth.

But these are the only two plants to gain a strong foothold in the swamp so far. Why? Is it because of the conditions here, which at times are decidedly untropical? On a winter day, the temperature can range from freezing to over seventy degrees farenheit; in summer the highs are much higher, the sun scorching at this altitude when the clouds have dissipated. The rainfall here is upwards of twenty feet a year. Rather than a true swamp, it is really a cloud forest, with most water provided in a constant dripping of condensation off the leaves, as opposed to torrential downpours.

Ohi`a, the dominant native plant, thrives under these conditions. It also thrives along the new lava flows of the kona coast of the Big Island, where barely a plant has yet gained traction, fresh water is only an occasional visitor, and the hard black lava radiates hundred-degree heat back on the trees from below. But you might suspect that a mutual transplant experiment would not work. The coastal Big Island ohi`a and the high-altitude Kaua`i ohi`a are two of dozens of subspecies of this plant classified within a mere three species, and they have clearly adapted to local conditions. But Hawaiian plants do not lend themselves easily to human-imposed Linnaean classification. The word "species" itself is completely inadequate to describe the multitudinous forms of life that occur in the world only on these islands.


To be continued...

Labels: environment, evolution, Hawaii, invasive species

I hope to continue this more regularly after a long hiatus. Heck, it's unclear whether anyone will ever read Bioblog anyhow, but then again, blogs are all about narcissism and self-deception anyway.

This article about "gay sheep" research in the New York Times has the ironic purpose of describing how the mainstream media distort science.

In this example, a quote by the researcher was taken completely out of its scientific context:

"The release quoted Dr. Roselli as saying that the research "also has broader implications for understanding the development and control of sexual motivation and mate selection across mammalian species, including humans.""

"Control," in Dr. Roselli's context, refers to how the brain controls behavior, given its anatomy and physiology. Yet of course media reports implied that the scientists were for some reason interested in "controlling" gay behavior - i.e. somehow figuring out how to "turn" gays into heterosexuals. According to the original paper referred to by the Times and presumably other articles, their interest is purely in the interaction of brain anatomy and animal behavior [ROSELLI et al, 2004. The Volume of a Sexually Dimorphic Nucleus in the Ovine Medial Preoptic Area/Anterior Hypothalamus Varies with Sexual Partner Preference. Endocrinology 145(2):478-483]:

__________

Similar to the results in humans, the variability in oSDN measurements
within each group of sheep was large compared with the differences
between groups, and it is impossible to predict the sexual
partner preference of any individual on the basis of a single
brain measurement. Nor do the present data allow us to
determine whether the observed differences in the size of the
oSDN are the cause or consequence of an animal's sexual
partner preference, or whether the size of the oSDN is influenced
by other unidentified variables. However, experiments
in several species (11) have shown that the development
of sexually dimorphic nuclei within MPOA/AH is the
direct result of exposure to testosterone or its metabolites
during a critical period in prenatal or early neonatal life.
Although it seems likely that the size of the SDN in sheep is
also established by testosterone exposure early, this relationship
has not yet been established.

_____


In other words, the authors are careful to point out the chicken-and-egg problem of correlating brain structure with behavior: innate structural differences can affect behavior, but lifetime experience can alter brain structure itself (how else would we be able to store memories?). This is why media accounts of gender studies showing "genetic" differences between males and females get my hackles up - by the time a baby is born, its environment (starting day 1 in the womb) has already affected its development.

Why study "gay" animal behavior if you don't have some sort of political agenda? I can give one good reason, off the top of my head. Many behavioral traits are very difficult to quantify and correlate with brain structure. Homosexual behavior is easy to study as a clear either-or behavior (at least in this case). Why not go for the slam-dunk of really being able to correlate specific behavior with a brain structure? Because it's cool. That's why scientists do their research - because it's cool. I guarantee you it isn't for the money. But of course a brush with fame is tempting, and we all want the world to know that our research is cool. Unfortunately many scientists, not really aware of life outside their ivory lab, get excited about the media attention without realizing how it can get out of control when a hotbed topic is concerned. I had a friend in grad school who studied sex in nematodes. When he discovered that male nematodes that never had sex lived longer than male nematodes that did, it wasn't just in the Science Times, it hit the front page (which was OK with him). What does nematode biology have to do with humans? Absolutely nothing. But sex sells.

In my own case, a Science paper on a topic less sexy but of burgeoning importance to environmentalists, nontarget attacks by biological control agents, led to an NPR interview, and I discovered how that works: all the intelligent things you say during the interview come out of the interviewer's mouth in the finished piece, and all the dorky things are when you are actually talking.

Labels: brain, evolution, health