Wednesday, October 5, 2016

Bee vs. Bee

I have this desire to grow my hair out and wear it in long white braids.

The U.S. Fish and Wildlife Service has given endangered status to seven species of bees from the genus Hylaeus (yellow-faced bees) native to the Hawaiian Islands. These species were not the first Species of bee proposed for listing as endangered; the patched bumble bee (Bombus affinis) was proposed earlier than the 2009 petition for the Hawaiian Hylaeus species. This first listing of a bee has been widely, but erroneously, linked to the perceived decline of commercial honeybees (Apis melifora) in the US.

The factors putting pressure on honeybees are not the same as those endangering the Hawaiian yellow-faced bee species. In fact, honeybees themselves are considered to be a significant contributing factor in the decline of the native bees. This is in stark contrast to the perceived notion that neonicotinoid pesticides are to blame for most bee problems. I have written earlier about the lack of measurable decline in honeybee populations in the US; bee populations actually have been increasing, and are now the highest (2014 was a 20 year high) they have been in decades.

A major factor in the more rapid listing of the seven Hylaeus species as endangered is the biology linked to two unique aspects of evolution. Foster’s rule (or “Island effect”) where perturbations in competitive pressures leads to unique evolutionary outcomes for isolated species. The other are the unique evolutionary outcomes caused by plant-pollinator mutualism. These mechanisms synergistically resulted in an evolutionary démarche that shaped the newly listed Hylaeus species into unique cogs of a wonderful tropical ecology

Another factor is the well written petition(s) prepared by members (Lisa Schonberg, Sarina Jepsen, and Scott Hoffman Black) of the Hawaiian Xerces society. Lisa plays drums in the “Secret Drum Band” which performs rather spacey music that probably went over very well in Portland where they recently toured.

“On the infrequent occasions when I have been called upon in a formal place to play the bongo drums, the introducer never seems to find it necessary to mention that I also do theoretical physics.” --statement by Richard Feynman after an introduction mentioning that he played bongo drums; Messenger Lectures at Cornell University

The petition(s) drove home the potential impact of extinction of these particular bee species on the overall ecology of a specific area. Extinction of a particular bee species can mean extinction of the plant it is mutualistically tied to. Lose the specialized pollinator and you lose the plant which requires a specialized pollinator in order to reproduce.

Solitary bees need to do all of the tasks required for survival of their nest with limited resources, and so they cannot afford many failures when attempting to perform those tasks. Eusocial bees, like the honeybee, can have a significant failure rate since there are many members of the hive attempting the same task. If a bee goes out in search of nectar or pollen it can search large areas that might not be productive if it is a honeybee, but the solitary bee must confine its search to areas with a higher potential for success; if the solitary bee fails at finding nectar it has spent valuable food resources and this might negatively impact its reproduction success.

Honeybees have the added selective advantage of learning as a hive; the worker that successfully finds nectar or pollen communicates the location of that find to the hive using a dance. So a single honeybee finding a flowering plant might result in hundreds of honeybees draining all the nectar from all the flowers on that plant; while the discovery of a flowering plant by a solitary bee would not bring additional bees to the plant.

Honeybees go after any source of food they can find, and have been observed feeding at plants that are also fed at by the yellow-faced bees. They therefore compete directly with them for sustenance.

“This study reports the results of an experiment run over two years on the impact of commercial honey bees on the fecundity of a solitary native bee, Hylaeus alcyoneus. Registered apiary sites were used as treatment sites (with honey bees) while control sites (without honey bees) were interspersed between. The fecundity of H. alcyoneus was measured using trap nests. We compared the number of nests produced, number of eggs per nest and emerging progeny mass of H. alcyoneus in sites with and without commercial bee hives. The number of nests produced by H. alcyoneus was 23% less (Wilcoxon’s T) at treatment sites than control sites.” -- Paini, Dean R. and Roberts, J. Dale. (2005) Commercial honey bees (Apis mellifera) reduce the fecundity of an Australian native bee (Hylaeus alcyoneus). Biological Conservation Volume 123, Issue 1, May 2005, Pages 103–112

The species of the genus Hylaeus look a lot like wasps, and use a specialized crop for carrying pollen. The seven Hawaiian species of Hylaeus that were listed as endangered also display some of characteristics of mutualism-induced phonotypic specialization. Hylaeus mana, for instance, has evolved into a very tiny bee capable of dropping into the specialized flowers of the parasitic forest sandalwood plant (Santalum freycinetianum).

Hylaeus mana is so small, and the flowers it feeds at so limited, that it was not described until 2002. It had just avoided notice.  Only four specimens have been collected.

The mutualistic evolution of plant-pollinator pairs provides benefits to both. The specialized pollinator –often a solitary bee- almost exclusively feeds at the specialized flower, and it therefore would most likely be carrying pollen from that species of flower to another of the same species. A general pollinator –like the honeybee- would most likely be carrying pollen from whatever was the most abundant flower at the time, and for rare flowers this is most likely not pollen from other flowers of that rare species. The plant in a plant-pollinator pair often evolves the ability to display specific attractants (like the wonderful smells and colors many flowers have) that improve the chances of a specialized pollinator being successful in finding food by finding it.

The specializations and attractants from these mutualistic pairings have created some of the most beautiful things on our planet.

Honeybee competition can result in a vicious feedback loop. They over-graze a specialized plant, and that reduces the reproductive success of the specialized pollinator. This causes a reduction in the specialized pollinator, which reduces the reproductive success of the specialized plant. Less of the specialized food source increases the effect of honeybee competition, and this can cause both the plant and specialized pollinator to spiral into extinction.

The Xerces society petition(s) also describe predation by ants and parasitism by wasps. The prioritization of ecological factors appear heavily weighted towards actions by members of the order Hymenoptera. This may be due in part to the shadow cast by Roy Snelling who died just months before the petition(s) was delivered.

Roy Snelling was a curmudgeonly self-taught entomologist and loud outspoken Atheist who wore his hair in long gray braids and would talk to anyone about the insects that captured his focus for most of the 73 years of his life. He studied all things Hymenoptera, and, though he was employed in Los Angeles at the Natural History Museum there, had a fondness for the bees and ants of the Hawaiian Islands. He described the competition between honeybees and solitary bees. He had also discovered new species of bees and ants. On April 23rd of 2008 he died in his sleep of a heart attack while on safari in Kenya looking for more Hymenoptera.

The problem with this story. This story that is literally about the bees doing the things that make for the better part of the “birds and bees” idiom. This story where long-haired thinkers dance crazily to spacey drum accompaniment through sandalwood scented forests of a tropical paradise. This story where a reasoned petition wins the glacial support of government conservation rules. The problem with this story is that the bees are killing bees; there is no Monsatan or cardboard villain who simplistically decimates the universe in an accelerating bid to increase its evil. We cannot easily partisanize this story in the way an election year requires of everything.

But come November we will again be living in the beautiful complex world of scents and buzzing that makes the study of ecological-evolutionary biology resonate within that thin film that supports life as we know it on this blue sphere of a planet we call Earth. Recognizing how those interactions get out of whack and doing something about the more fragile margins will make future Novembers a little more beautiful.

1 comment:

Kimberly Wilson said...