The Moss Lab
Reproductive Behavior and Evolution
Sex in Changing Environments
(C) Geoff While
Anthropogenic environmental changes are causing dramatic shifts in the spatial and temporal arrangement of organisms and their behavior, with important ramifications for mating and social systems. Research in the Moss lab aims to generate both a theoretical and empirical foundation from which to explore these outcomes.
Previous Work
In today's world, longitudinal natural population datasets provide invaluable resources for tracking organismal responses to environmental change. Jen's dissertation research examined how human habitation is impacting demographic and evolutionary potentials of a critically endangered lizard, the Sister Islands Rock Iguana. Through a combination of mark-recapture surveys, nest excavations, drone-assisted radio telemetry, and genetic analysis, this work revealed synergistic effects of natal microenvironment and inbreeding level on offspring performance.
(C) Mikey Kartje
A second key outcome was that female mating and nesting strategies that shape conditions for developing embryos are highly contingent on social conditions experienced during the reproductive season. Thus, the key to understanding the repercussions of human land use for the most vulnerable age classes lies in understanding its effects on distributions and interactions among adults.
One environmental variable with the potential to dramatically restructure animal social interactions is temperature. Indeed, the thermal environment has a massive impact on every facet of animal life, particularly behavior. That’s because most animals are ectothermic, meaning the primary way they deal with temperature change on a day-to-day basis is through behavioral thermoregulation – adjusting their activity to exploit optimal thermal conditions and avoid suboptimal thermal conditions.
As an Endeavour Postdoctoral Fellow at the University of Tasmania, Australia, Jen collaborated with Dr. Geoff While to develop a framework for studying how the thermal environment may mediate social transformations at various evolutionary stages. In an ambitious experiment involving lizards (Liopholis whitii) and semi-natural mesocosms, the team then went about testing these ideas by manipulating the thermal conditions experienced by replicated populations over the course of the breeding season. Their prediction was that warmer temperatures would promote higher activity (because Tasmania is temperate and spring are typically cooler) which would allow for higher rates of mating and, ultimately, shifts in the strength and targets of sexual selection. What they instead found was that more restrictive thermal regimes subject activity to stronger fecundity selection on females, but not sexual selection on males (Fig 1). Because reproductive outcomes for males and females are inextricably linked, this suggests that underlying sex differences may constrain the ability of a population to respond to temperature even after accounting for behavioral plasticity at the individual level.
Figure 1: Temperature-dependent shifts in reproductive rates (A) and subsequent fecundity (B) and sexual selection (C) on individual activity in a mesocosm experiment.
Next Steps
Future work in the Moss Lab will combine natural population monitoring with rigorous field and laboratory experiments to explore how sex differences in plasticity are shaping demographic and evolutionary responses to climate change. Plethodontid salamanders in Appalachia are finely adapted to cool, montane environments and rely on climatic cues to guide their above-ground activity patterns. Under future climate projections, longer growing seasons and shorter, milder winters could enhance fitness via increases in foraging times, energy budgets, and mating opportunities. However, given sexual dimorphism in how and when energy is allocated to reproduction, we may expect males and females to show distinct plastic responses to warming.
(C) A. & R. Simpson
In our new lab at Virginia Tech, we will leverage a locally abundant and experimentally tractable species, Plethodon cinereus, to study the links between thermal plasticity at the individual level, sex-specific reproductive strategies and outcomes, and selection on male and female traits. We will also be taking advantage of some fascinating aspects of this species' biology, such as long-term sperm storage, to explore the consequences of warming winters for post-copulatory sexual selection.