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Publications by EEOB faculty May 1 - May 31

May 30, 2017

Publications by EEOB faculty May 1 - May 31

EEOB graphic 2016

Evaluating local adaptation of a complex phenotype: reciprocal tests of pigmy rattlesnake venoms on treefrog prey

Smiley-Walters, S.A., Farrell, T.M. & Gibbs, H.L. Oecologia (2017). doi:10.1007/s00442-017-3882-8
 
Abstract
 
Theory predicts that predator–prey interactions can generate reciprocal selection pressures on species pairs, which can result in local adaptation, yet the presence and pattern of local adaptation is poorly studied in vertebrate predator–prey systems. Here, we used a reciprocal common garden (laboratory) experimental design involving comparisons between local and foreign populations to determine if local adaptation was present between a generalist predator—the pigmy rattlesnake (Sistrurus miliarius)—and a co-occurring prey—the squirrel treefrog (Hyla squirella). We conducted toxicity trials using snake venom from two populations separated by 340 km tested on prey from sympatric and allopatric populations, resulting in data from four venom origin–frog origin combinations. We assessed venom effectiveness using two measures (frog mortality at 24 h and time to frog death) and then used regression analyses to look for a signal of local adaptation with either measure. We found evidence for local adaptation for one measure (time to death), but not the other (frog mortality). We argue that in this system, the time to death of a prey item is a more ecologically relevant measure of venom effectiveness than is frog mortality at 24 h. Our results document an example of local adaptation between two interacting vertebrates using a whole-organism assay and a local versus foreign criteria and provide evidence that population-level variation in snake venom is adaptive.

Isotocin neuronal phenotypes differ among social systems in cichlid fishes

Adam R. Reddon, Constance M. O'Connor, Erin Nesjan, Jason Cameron, Jennifer K. Hellmann, Isaac Y. Ligocki, Susan E. Marsh-Rollo, Ian M. Hamilton, Douglas R. Wylie, Peter L. Hurd, Sigal Balshine. 2017. DOI: 10.1098/rsos.170350
 
Abstract
 
Social living has evolved numerous times across a diverse array of animal taxa. An open question is how the transition to a social lifestyle has shaped, and been shaped by, the underlying neurohormonal machinery of social behaviour. The nonapeptide neurohormones, implicated in the regulation of social behaviours, are prime candidates for the neuroendocrine substrates of social evolution. Here, we examined the brains of eight cichlid fish species with divergent social systems, comparing the number and size of preoptic neurons that express the nonapeptides isotocin and vasotocin. While controlling for the influence of phylogeny and body size, we found that the highly social cooperatively breeding species (n = 4) had fewer parvocellular isotocin neurons than the less social independently breeding species (n = 4), suggesting that the evolutionary transition to group living and cooperative breeding was associated with a reduction in the number of these neurons. In a complementary analysis, we found that the size and number of isotocin neurons significantly differentiated the cooperatively breeding from the independently breeding species. Our results suggest that isotocin is related to sociality in cichlids and may provide a mechanistic substrate for the evolution of sociality.

Novel mandibular gland volatiles from Apterostigma ants

Conor T. Hogana, Tappey H. Jonesb, Mariya Zhukovac, Jeffrey Sosa-Calvod, Rachelle M.M. Adams. 2017. Biochemical Systematics and Ecology. 72(56–62).

Abstract

The fungus-farming ants are a well-studied evolutionary radiation within the subfamily Myrmicinae that associate with a web of symbionts that span kingdoms. Members of the Apterostigma pilosum species group cultivate unique basidiomycete fungi belonging to the coral-mushroom family Pterulaceae, a family of fungi that is distantly related to the Agaricaceae (Leucoagaricus and Leucocoprinus) fungi grown by most fungus-farmers including other members in the genus Apterostigma (A. auriculatum group and A. megacephala). A chemical analysis using gas chromatography–mass spectroscopy of the mandibular gland volatiles of two species – A. dentigerum and A. manni – revealed the presence of an extraordinary diversity of natural products. Many of these compounds are new to Arthropoda, such as a homologous series of 3-methyl-2-alkanones, 2-methyl-2-alkenals, and 1-phenyl-2-propanone in A. dentigerum and 1-phenyl-2-propanol in A. manni. These results identify a remarkable divergence of compounds across the fungus-growing ants and other members in Myrmicinae. Functions of these natural products are proposed and discussed.


Climate change as a long-term stressor for the fisheries of the Laurentian Great Lakes of North America

Paris D. Collingsworth, David B. Bunnell, Michael W. Murray, Yu-Chun Kao, Zachary S. Feiner, Randall M. Claramunt, Brent M. Lofgren, Tomas O. Höök, Stuart A. Ludsin. Rev Fish Biol Fisheries (2017). doi:10.1007/s11160-017-9480-3

Abstract

The Laurentian Great Lakes of North America provide valuable ecosystem services, including fisheries, to the surrounding population. Given the prevalence of other anthropogenic stressors that have historically affected the fisheries of the Great Lakes (e.g., eutrophication, invasive species, overfishing), climate change is often viewed as a long-term stressor and, subsequently, may not always be prioritized by managers and researchers. However, climate change has the potential to negatively affect fish and fisheries in the Great Lakes through its influence on habitat. In this paper, we (1) summarize projected changes in climate and fish habitat in the Great Lakes; (2) summarize fish responses to climate change in the Great Lakes; (3) describe key interactions between climate change and other stressors relevant to Great Lakes fish, and (4) summarize how climate change can be incorporated into fisheries management. In general, fish habitat is projected to be characterized by warmer temperatures throughout the water column, less ice cover, longer periods of stratification, and more frequent and widespread periods of bottom hypoxia in productive areas of the Great Lakes. Based solely on thermal habitat, fish populations theoretically could experience prolonged optimal growth environment within a changing climate, however, models that assess physical habitat influences at specific life stages convey a more complex picture. Looking at specific interactions with other stressors, climate change may exacerbate the negative impacts of both eutrophication and invasive species for fish habitat in the Great Lakes. Although expanding monitoring and research to consider climate change interactions with currently studied stressors, may offer managers the best opportunity to keep the valuable Great Lakes fisheries sustainable, this expansion is globally applicable for large lake ecosystem dealing with multiple stressors in the face of continued human-driven changes.
 

Endemic diversification in an isolated archipelago with few endemics: an example from a cleaner shrimp species complex in the Tropical Western Atlantic

Benjamin M. Titus, Spencer Palombit, Marymegan Daly. 2017. Biol J Linn Soc. doi: 10.1093/biolinnean/blx039

Abstract

Isolated oceanic islands are important sources of evolutionary novelty and typically have an increased prevalence of endemism. The tropical, shallow-water community of the Bermudan archipelago is unique, however, in that it has lower rates of endemism than its isolation would suggest. Here we investigate a species complex of cleaner shrimp in the genus Ancylomenes (Decapoda: Palaemonidae) for which there has been (1) uncertainty over the morphological description of the Bermudan shrimp as a true endemic and (2) conflicting accounts of its ecological associations. We use multi-locus sequence data, molecular species delimitation, phylogenetic analyses and ecological observations to test the hypothesis that the Bermudan cleaner shrimp, Ancylomenes anthophilus, is a true endemic warranting its current morphological description. Although our nuclear marker provided little resolution, A. anthophilus was reciprocally monophyletic at two mitochondrial loci, and species delimitation analyses support the distinction of A. anthophilus as a true endemic across the full data set. Phylogenetic and coalescent analyses suggest that A. anthophilus split from the widespread Ancylomenes pedersoni and arrived in Bermuda during the Pleistocene (~1.5–2.9 Myr). The pattern recovered in our molecular analyses, suggests that A. anthophilus likely diversified in isolation after arriving from the Caribbean via a chance, long-distance colonization event after the formation of the Gulf Stream. A Pleistocene origin for A. anthophilus implies that it persisted through a period of major environmental variation.