Evolution Ultragroup

This week we will be back in the normal room – Yates 206 – and will hear a talk by PhD student Corey Handelsman. He will present research on Trinidadian guppies that is being conducted by himself, Julian Torres Dowdall, Dr. Cameron Ghalambor and many others – including a lab component at CSU and fieldwork in Trinidad.

Mechanisms of local adaptation in Trinidadian guppies (Poecilia reticulata)

Abstract: Natural selection is one of several key mechanisms driving the diversification of organisms. However, despite laboratory experiments frequently demonstrating the potential for traits to undergo selection, detecting selection in the wild is far less frequent. The failure to detect selection in the wild is likely due to the various limitations associated with obtaining quantitative data on performance traits for natural populations over time. Previous work with Trinidadian guppies from high and low predation populations has shown that evolution can proceed far faster than previously thought and, for life history traits, occurs on ecological time scales. Although these evolutionary patterns are repeatable in guppy populations throughout Trinidad, the underlying mechanism of local adaptation remains elusive. Taking advantage of recent introduction experiments we are beginning to unravel the roles of phenotypic plasticity and directional selection in local adaptation. Through a combination of laboratory experiments and field observations, heritabilities and plasticity in morphology, performance and life history traits are being measured and used to make predictions on how populations respond during the early stages of evolutionary divergence.

This week’s seminar will be given by Charles Stone, a PhD student working with Dr. Janice Moore. There is a slight change of venue, as a faculty meeting has been scheduled in the room we normally use, so for this week – and this week only – please come to Yates 208. Here’s a title and brief abstract for Charles’ talk:

Does size matter? Fitness, larval size, and strange behavior related to the Acanthocephalan parasite Leptorhynchoides thecatus

Abstract: Modification of host behavior by parasites has been documented in a large variety of parasite systems. To understand how these phenomena evolve and operate, scientists have developed models and theoretical frameworks. Much of this literature explicitly assumes that there is a cost to a parasite when it actively changes host behavior, despite the fact that no study has demonstrated such a cost. The parasite Leptorhynchoides thecatus (Acanthocephala) presents an opportunity to investigate such a cost. Smaller larval cystacanths are less likely to survive transmission to the final host and establish as adults. Because transmission and establishment success are essential components of fitness, parasite larval size provides an important potential link to a fitness cost if behavioral modification is related to larval size. In this study, behavioral changes were demonstrated in a series of three behavioral tests on the crustacean intermediate host, Hyalella azteca (Amphipoda). Behavioral scores compared between infected and uninfected hosts show significant differences in behavior between groups. When infected amphipod behavior was considered in relation to parasite volume, none of the behaviors showed a strong influence of larval size. These results may be explained by a number of factors, which will be highlighted for future directions for this research.