Does habitat disturbance promote geographical parthenogenesis in whiptail lizards?

Authors: COSENTINO, BRADLEY - Hobart College; SCHOOLEY, ROBERT - University Of Illinois; Bestelmeyer, Brandon; CAMPOS, HERMAN - New Mexico State University; Burkett, Laura

Submitted to: Evolutionary Ecology Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2019
Publication Date: 9/4/2019
Citation: Cosentino, B., Schooley, R., Bestelmeyer, B.T., Campos, H., Burkett, L.M. 2019. Does habitat disturbance promote geographical parthenogenesis in whiptail lizards?. Evolutionary Ecology Research. 33:839-853. https://doi.org/10.1007/s10682-019-10006-3.
DOI: https://doi.org/10.1007/s10682-019-10006-3

Interpretive Summary: Parthenogens (animal species that reproduce via unfertilized eggs) are hypothesized to be favored in harsher environments because sexual forms of the same species outcompete them in more favorable habitats and parthenogens disperse more readily. We used a landscape-scale field experiment in the Chihuahuan Desert to test whether parthenogenetic whiptail lizards (Aspidoscelis spp.) were favored in areas where shrubs were present (more favorable habitat) compared to where they were removed. We found that parthenogenetic and sexual species both responded positively to habitat disturbance, but only when the other whiptail species' abundance was low. The positive response of both species to shrub removal, along with a remarkable checkerboard pattern of abundances, showed that the parthenogen is not occupying disturbed habitat simply to avoid competition with sexuals. In our study system, the parthenogen often dominates older disturbed sites, especially two decades or more after shrub removal, suggesting geographical parthenogenesis emerges from parthenogens eventually outcompeting their sexual congeners.

Technical Abstract: Geographical parthenogenesis refers to parthenogenetic organisms occurring more frequently at range margins and in disturbed habitats compared to their sexual relatives. Hypotheses to explain geographical parthenogenesis focus on the greater colonizing ability of parthenogens than sexuals, and the avoidance of competition with sexuals by inhabiting marginal ecological conditions. Yet theory predicts parthenogens can outcompete sexuals when clonal diversity is high or resource utilization is highly plastic. We used a landscape-scale field experiment in the Chihuahuan Desert to test whether competition between parthenogenetic and sexual whiptail lizards (Aspidoscelis spp.) mediates their response to widespread vegetation disturbance from shrub removal. Using a novel co-abundance model that accounts for imperfect detection, we found the parthenogenetic A. uniparens and sexual A. marmorata both responded positively to habitat disturbance, but only when the congener’s abundance was low. The positive response of both species to disturbance, along with a remarkable checkerboard pattern of abundances, showed that the parthenogen is not occupying disturbed habitat simply to avoid competition with sexuals. In our study system, A. uniparens often dominates older disturbed sites, especially two decades or more after shrub removal, suggesting geographical parthenogenesis emerges from parthenogens eventually outcompeting their sexual congeners.