Phylogenetically independent behavior mediating geographic distributions suggests habitat is a strong driver of phenotype in crangonyctid amphipods

It is unclear if geographic distributions of animals are behaviorally mediated or simply maintained by ecologically-driven deleterious effects on fitness. Furthermore, it is not well known how behaviors that may affect geographic distributions and responses to environmental stressors evolve. To explore this, we examined behavioral and physiological reactions to light in six species of amphipods in the family Crangonyctidae collected from a variety of subterranean and epigean habitats. Stark differences between epigean and subterranean habitats occupied by different crangonyctid species allowed this clade to serve as an appropriate model system for studying the link between habitat and phenotype. We sampled habitats in or adjacent to the Edwards Aquifer in central Texas and collected two epigean and four stygobiontic species. We examined respiratory and behavioral responses to light in all study species. We found that similarities in behavioral and physiological responses to light between species were only weakly correlated with genetic relatedness but were correlated with habitat type. However, the breadth of variation in phenotype was found to be correlated with phylogenetic relationships, suggesting that population level trait evolution likely involves interactions between standing population level variation and strength of selection. Our findings suggest that natural selection via environmental conditions may outweigh history of common ancestry when predicting phenotypic similarities among species, and that behavioral and physiological phenotypes may mediate the evolution of biogeographic distributions

Fig 1 in Sexual Dimorphism in Three Species of Heterelmis Sharp (Coleoptera: Elmidae)

Fig 1. Heterelmis comalensis, representative female (a–c), and male (d–f) abdomens showing variation in length of the fifth (last) ventrite. Females are recognizable by noticeably more elongate fifth ventrite. Scale bar = 500 µm.Published as part of <i>Nair, Parvathi, Hunter, Amelia H., Worsham, McLean L. D., Stehle, Matthew, Gibson, J. Randy & Nowlin, Weston H., 2019, Sexual Dimorphism in Three Species of Heterelmis Sharp (Coleoptera: Elmidae), pp. 1075-1083 in The Coleopterists Bulletin 73 (4)</i> on page 1079, DOI: 10.1649/0010-065X-73.4.1075, <a href="http://zenodo.org/record/10113980">http://zenodo.org/record/10113980</a&gt

Sexual Dimorphism in Three Species of Heterelmis Sharp (Coleoptera: Elmidae)

Nair, Parvathi, Hunter, Amelia H., Worsham, McLean L. D., Stehle, Matthew, Gibson, J. Randy, Nowlin, Weston H. (2019): Sexual Dimorphism in Three Species of Heterelmis Sharp (Coleoptera: Elmidae). The Coleopterists Bulletin 73 (4): 1075-1083, DOI: 10.1649/0010-065X-73.4.1075, URL: http://dx.doi.org/10.1649/0010-065x-73.4.107

Fig. 4 in Sexual Dimorphism in Three Species of Heterelmis Sharp (Coleoptera: Elmidae)

Fig. 4. Observed frequency distributions of three body characteristics of male and female Heterelmis vulnerata (n = 61 individuals). a) Total body length (in mm), b) Abdominal length (in mm), c) Fifth ventrite length (in mm). The vertical dashed line in panel c is a proposed fifth ventrite size threshold (0.26 mm) that could be used to determine sex using this feature.Published as part of <i>Nair, Parvathi, Hunter, Amelia H., Worsham, McLean L. D., Stehle, Matthew, Gibson, J. Randy & Nowlin, Weston H., 2019, Sexual Dimorphism in Three Species of Heterelmis Sharp (Coleoptera: Elmidae), pp. 1075-1083 in The Coleopterists Bulletin 73 (4)</i> on page 1081, DOI: 10.1649/0010-065X-73.4.1075, <a href="http://zenodo.org/record/10113980">http://zenodo.org/record/10113980</a&gt