After working very hard this winter to submit a manuscript describing the most recent results of the project, I realized that it has really become two non-overlapping lines of inquiry.

A few weeks ago, I submitted a manuscript titled “Batesian Mimicry and Thermal Resilience Among Tenebrionid Beetles from a New Mexican Piñon-Juniper Savanna” to the Journal of Experimental Biology. The editor said some kind words about it, but ultimately rejected it because it did not fit comfortably into the aims of the journal. The main complaint was that a significant portion of the paper focused on the ecology of the beetles, rather than their physiology.

It took a few days for me to realize that the paper had evolved into something different. Looking over the title, two things may stand out.

Batesian Mimicry

Thermal Resilience

Those are really two separate concepts and analyzing either one can be performed relatively independently of the other. In other words, this was two incomplete papers rather than one solid story.

Now begins the process of completing both of those stories.

Mimicry

Several lines of evidence address whether the Asidini Philolithus elatus and Stenomorpha rimata are Batesian mimics of the Amphidorine Eleodes obscura. For an organism to be a bona fide Batesian mimic it must

• Resemble the model in the eyes (or ears or nose) of potential predators.
• Be palatable
• Be undefended (or at least to a potential predator)
• Overlap the model in space and/or time so that predators can learn the association
• Be relatively uncommon to prevent predators from discovering their mimicry

The Asidini fulfill these criteria to varying degrees

• The major argument for mimicry is that the Asidini look a lot like E. obscura, and are about the same size and mass.
• A close relative of S. rimata, S. marginata, has been shown to be palatable to mice and skunks. Palatability of P. elatus is unknown.

On the minus side:

• P. elatus will regurgitate when handled, suggesting at least mild defense
• Headstanding behavior, which contributes to the mimicry, is weak (P. elatus) or non-existent (S. rimata)
• Both Asidini are at least as common as E. obscura during peak season, giving predators plenty of opportunity to learn that they are quite edible.
• Stenomorpha rimata is present in late September and October, when Eleodes have disappeared from the surface, giving predators plenty of time to learn that they are tasty and undefended.

I really need to know who the local predators are, so that I can make sense of all this. I hope to use the upcoming field season to find out who is eating beetles around here. Based on scats and scattered body parts, someone is eating them, but who?

Thermal Resilience

Maintenance of scent glands is costly, so E. obscura should either use more metabolic energy than the undefended P. elatus and S. rimata, or devote less energy to other aspects of fitness. Based on respirometry across a range of temperatures it would appear that all three species use the same amount of energy per unit time, but the Asidini have much higher survival at elevated temperatures.

This is a nice partial story, but I need to know more about possible mechanisms. Two sets of experiments would be very ,helpful in completing this part of the story.

• Testing survival across a full range of temperatures. I have only tested up to 40C, which is semi-lethal to Eleodes but does not strongly affect P. elatus or S. rimata. Although I am no fond of the idea, I need to test up to a temperature that is 100% lethal in order to have a complete picture of thermal resilience.
• Because temperature induced lethality is associated with disrupted ionic regulation, it will be important to examine concentrations of ions in the hemolymph (blood) of E. obscura, P. elatus and S. rimata at high temperatures.

If all goes well, I should have two papers ready by the end of the season. Wish me luck.