Biology subjects

Stuart, Y. E.

Publications and source records attributed to Stuart, Y. E..

3 recordsLinked to original sources

bioRxiv2023

Predictable and divergent change in the multivariate P-matrix during parallel adaptation

AbstractAdaptation to replicated environmental conditions can be remarkably predictable, suggesting parallel evolution may be a common feature of adaptive radiation. An open question, however, is how phenotypic variation itself evolves during repeated adaptation. Here, we use a dataset of morphological measurements from 35 populations of threespine stickleback, consisting of 16 parapatric lake- stream pairs and three marine populations, to understand how phenotypic variation has evolved during transitions from marine to freshwater environments, and during subsequent diversification across the lake-stream boundary. We find statistical support for divergent phenotypic covariance (P) across populations, with most diversification of P occurring across freshwater populations. Despite a close correspondence between within-population phenotypic variation and among population divergence, we find that variation in P is unrelated to total variation in population means across the set of populations. Within lake-stream pairs, however, we find that theoretical predictions for microevolutionary change can explain over 30% of the total divergence in P matrices across the habitat boundary. Together, our results indicate that variance evolution occurs primarily in dimensions of trait space with low phenotypic integration, driven by divergence into disparate lake and stream environments, illustrating how conserved and divergent features of multivariate variation can underlie adaptive radiation.

evolutionary biology↗

bioRxiv2023

A resurrection ecology test for the effects of ionizing radiation and other environmental correlates on Daphnia evolution

Acute exposure to ionizing radiation has well-documented, immediate negative consequences for individuals. However, the evolutionary consequences for populations exposed to ionizing radiation is unclear. For example, a meta-analysis of taxa exposed to Chernobyl fallout found some evidence for elevated mutation rates in animal and plant taxa; however, in people, de novo mutation rates in offspring of parents exposed to radiation during and after the Chernobyl accident were no higher than controls. Furthermore, whether irradiation and increased mutation rates drive adaptation to radiation also has mixed support. Ambiguity in both cases likely arises from the difficulty of studying mutation rates and adaptation after rare nuclear events whose ionizing radiation is distributed heterogeneously in time and space. Here, we report an attempt to better address this difficulty with a "resurrection ecology" study of Daphnia spp. in Utah lakes that experienced nuclear fallout from US Department of Energy weapons testing in the 1950s and 1960s. The idea was to recover dormant Daphnia eggs from sediment cores that spanned the nuclear testing era in the American West. We predicted that survival and fecundity of eggs hatched in the lab would show fitness declines correlated with ionizing radiation fallout and a potential recovery once nuclear testing stopped. We successfully obtained multiple cores from three lakes that dated back to the 1800s. We isolated >4700 dormant eggs from those cores, spanning the nuclear era, but were only able to hatch a single egg in the lab. Thus, we could not conduct life history experiments to test our prediction. The purpose of this manuscript, therefore, is to describe the study and make our radioisotope core dating and sedimentation data available to other paleolimnological researchers. We also report a side study of stable isotope change through time measured from dormant eggs and the sediment.

evolutionary biology↗

bioRxiv2019

Repeatability of adaptive radiation depends on spatial scale: regional versus global replicates of stickleback in lake versus stream habitats

The repeatability of adaptive radiation is expected to be scale dependent, with determinism decreasing as greater spatial separation among "replicates" leads to their increased genetic and ecological independence. Threespine stickleback (Gasterosteus aculeatus) provide an opportunity to test whether this expectation holds for the early stages of adaptive radiation - their diversification in freshwater ecosystems has been replicated many times. To better understand the repeatability of that adaptive radiation, we examined the influence of geographic scale on levels of parallel evolution by quantifying phenotypic and genetic divergence between lake and stream stickleback pairs sampled at regional (Vancouver Island) and global (North America and Europe) scales. We measured phenotypes known to show lake-stream divergence and used reduced representation genome-wide sequencing to estimate genetic divergence. We assessed the scale-dependence of parallel evolution by comparing effect sizes from multivariate models and also the direction and magnitude of lake-stream divergence vectors. At the phenotypic level, parallelism was greater at the regional than the global scale. At the genetic level, putative selected loci showed greater lake-stream parallelism at the regional than the global scale. Generally, the level of parallel evolution was low at both scales, except for some key univariate traits. Divergence vectors were often orthogonal, highlighting possible ecological and genetic constraints on parallel evolution at both scales. Overall, our results confirm that the repeatability of adaptive radiation decreases at increasing spatial scales. We suggest that greater environmental heterogeneity at larger scales imposes different selection regimes, thus generating lower repeatability of adaptive radiation at larger spatial scales.

evolutionary biology↗