Comparative analysis of the costs of a sexually selected trait

        For my dissertation I am examining the effects of a sexually selected trait on locomotor performance. I am using the fish genus Xiphophorus  (swordtails and platyfish) as a model system and I am measuring various performances. I am looking at the effect the sexually selected "sword" has on escape response, sprint speed, and critical swimming speed. I am also examining potential compensatory mechanisms. That is, traits that may have co-evolved with the sword to offset its potential locomotor costs. Therefore I will also be examining maximum oxygen consumption (VO_2max), heart mass, gill mass and enzymes involved in both aerobic and anaerobic respiration. If the sword is costly in terms of locomotion, these traits may have coevolved to offset the cost, resulting in larger heart or gill mass or increased VO_2max. I am examining the whole genus of Xiphophorus including species with (e.g., X. helleri) and without (e.g. X. variatus) the trait. For more info. on this research see this paper for more detail:
Oufiero, C. E., and T. Garland, Jr. In press. Evaluating performance costs of sexually selected traits. Functional Ecology. pdf.

Individual variation and correlation of swimming performances

    In addition to examining the effect of a sexually selected trait on locomotor performance, I have also been conducting studies on 2 species of fish from the Poeciliidea to determine the amount of individual variation associated with each performance measure. To do this, I measured ~20 individual Trinidadian guppies (Poecilia reticulata) and platyfish (X. maculatus) 3 times for each performance (burst speed, escape response and critical swimming speed). I will also be looking at enzyme correlates as well as measuring each performance in the guppies an additional time, more than a year after initial measurements to determine long term individual variation.

 

Does community composition affect performance in Rivulus hartii?

    This project examines the effect of various community compositions on sprint speed and endurance in Hart's killifish (Rivulus hartii). R. hartii is an egg laying fish that occurs throughout the streams of Trinidad. Much work in this system has examined evolutionary changes in the guppy across sites that differ in predation intensity. However, Rivulus are also located in the same ‘high’ (HP) and ‘low’ (LP) predation sites as guppies, and due to a greater dispersal capability than all other species, Rivulus are also found in sites by themselves (R). The presence of predators has been shown to cause evolutionary shifts in performance. Therefore, the general prediction is that high predation fish should evolve to maximize their escape abilities, potentially at the compromise of their endurance. In contrast, fish in low predation sites should evolve higher endurance to maximize foraging, mating, etc. However, contrasting underlying ecological interactions between the fish communities that lack predators may have differential effects on performance. For instance, the density of Rivulus declines 3-fold in sites with guppies, preliminary evidence suggests that guppies prey upon larval Rivulus and both species compete for limited resources. Therefore, the predictions for the R and LP sites might not be as easy to disentangle because of these interactions. Using mature, wild caught, lab acclimated fish we tested whether the community composition of a species affects its performance. We measured the critical swimming speed (U_crit), sprint speed and body size of fish from 7 populations (3 R, 3 LP and 1 HP) in 3 river drainages. Preliminary analysis suggests that while there is no significant difference in U_crit between R and LP sites within and among rivers; the HP fish have a significantly lower U_crit than the R and LP sites, consistent with predictions.

Can fish correct their escape response in relation to consecutive stimulus?

As part of the fish swimming course I attended at Friday Harbor Laboratories in the San Juan Islands, WA, we examined whether fish were able to correct their escape response in relation to two stimulus. Fish were placed in the center of an arena and stimuli were dropped on either side of the fish consecutively. We tested the fish under three conditions, 30ms separation, 60ms, and control (only one stimulus). It seems that the fish exhibited a greater proportion of away responses in the control and 60ms group, but there was no difference in the proportion of towards or away response in the 30ms group. These results suggest that early in the initiation of the escape response a fish might not be able to correct its position, resulting in the randomness of towards vs. away response in the 30ms, as compared to the control or 60ms group.

Is scale number variation in Sceloporus an adaptive response to environment?

This research is using new phylogenetic statistical programs to determine if scale number variation is an adaptive response to the environment. It has been predicted that lizards inhabiting warmer/drier habitats would have fewer/larger scales to aid in heat dissipation. In contrast, lizards from colder environments are predicted to have more/smaller scales to aid in heat retention. Several studies have examined this, but have found mixed results. Therefore, using 106 species and populations from the lizard genus Sceloporus we looked at the relationship between midpoint latitude of a species range (as a proxy for environmental temperature) and scale number (as a proxy for scale size). Our results indicate that after controlling for phylogenetic relationships, lizards from more northern latitudes tend to have more scales, in accordance with predictions.

I conducted my Masters work at Indiana State University in Michael Angilletta's lab. I examined the evolution of growth and development in embryos of the eastern fence lizard (Sceloporus undulatus). I sampled five populations from two separate clades along a latitudinal gradient (NJ, VA, & SC; IN & FL). After rearing the embryos under two common (fluctuating) environments, I found that lizards from northern latitudes had faster development and higher growth efficiency. I also examined whether pelvic constraints or energetic constraints were more important in reproductive allocation of these five populations, the effects of natural fluctuating incubation environments on costs of development in embryos from New Jersey, and used path analysis and the Akaike Information Criterion to determine which model of optimal egg size was best supported by life history data from 18 populations of S. undulatus. Below is a list of publications generated from this work.

Oufiero, C.E., A.J. Smith and M.J. Angilletta. 2007. The importance of energetic versus pelvic constraints on reproductive allocation by the eastern fence lizard (Sceloporus undulatus). The Biological Journal of the Linnean Society 91: 513-521.

Angilletta, M.J., C.E. Oufiero and A.D. Leache. 2006. Direct and indirect effects of environmental temperature on the evolution of reproductive strategies: an information-theoretic approach. The American Naturalist 168: E123-E135. pdf.

Oufiero, C.E. and M.J. Angilletta. 2006. Convergent evolution of embryonic growth and development in the eastern fence lizard (Sceloporus undulatus). Evolution 60(5): 1066-1075. pdf.

 Angilletta, M.J., C.E. Oufiero, and M.W. Sears. 2004. Thermal adaptation of maternal and embryonic phenotypes in a geographically widespread lizard. Pp. 258-266 in S. Morris and  A. Vosloo, eds. Animals and Environments. Proceedings of the Third International Conference of Comparative Physiology and Biochemistry. Elsevier Press. pdf.