Biology subjects

Reznick, D. N.

Publications and source records attributed to Reznick, D. N..

5 recordsLinked to original sources

bioRxiv2026

Competition among kin generates balancing selection in a wild population

If an individuals niche is determined by its genotype, then competition for limiting resources should be most intense among individuals of the same genotype. Theory predicts this will act to maintain genetic variation, but whether this mechanism operates under natural conditions is unclear. Using long-term observations of a population of free-living Trinidadian guppies, we asked (i) whether competition was strongest between kin, and (ii) whether this process maintained genetic variation. Competition between kin was 1.5-1.8 times stronger than that between non-kin. This contributed to balancing selection: after [~]10 generations, variation was 29% higher than expected under drift. Our results show that relatedness can play a major role in structuring ecological competition, with broader consequences for theories of inclusive fitness. One-sentence summaryHeritable variation is maintained due to resource competition being more intense among kin.

evolutionary biology↗

bioRxiv2026

Temporal genomics reveals rapid parallel adaptation in experimental populations of Trinidadian guppies (Poecilia reticulata)

Understanding the genomic basis of early adaptation is a central question in evolutionary biology. Although there is ongoing debate about whether early adaptation is more likely to be driven by polygenic responses or by loci of large effect, few studies of natural populations have been able to address this problem. Furthermore, early adaptation to a novel environment often coincides with founding events, making it difficult to disentangle neutral effects from adaptive genomic changes. Here we take advantage of the unique in situ guppy experimental system, in which we established replicate populations by translocating guppies from a high predation locality to four low predation localities. We present whole genome sequencing from the source population and the four experimental populations, sampled after [~]8-10 generations (first period), and again at [~]18-22 generations (second period). We find signatures of inbreeding only in the first period, despite documented population crashes in the second period. We show genome-wide dynamics of selection as well as selective change at single loci and uncover new targets of selection. Overall, we found signatures of selection at all levels; genome-wide, chromosome, and individual windows are more repeatable among replicates in the first period than in the second period.

evolutionary biology↗

bioRxiv2021

Life histories as mosaics: plastic and genetic components differ among traits that underpin life-history strategies

Life-history variation reflects phenotypic variation across suites of traits. Differences among life-history strategies result from genetic differentiation, phenotypic plasticity, and genotype-by-environment interactions. If the relative strength and direction of these components differed among traits underlying a strategy, life histories might not evolve as a cohesive unit. We tested this hypothesis on the high- and low-predation ecotypes of Trinidadian guppies, defined by distinct life-history strategies. Using common garden experiments, we assessed how strongly 36 traits were determined by ancestral habitat (i.e., ecotype) or food availability, a key environmental difference between ecotypes. Our dataset was large (1178 individuals) and included six putatively independent origins of the derived ecotype. Traits could be confidently assigned to four groups, defined by highly significant effects of only food (13 traits), only habitat (6), both (6), or neither (11), revealing substantial variation among traits in levels of genetic and environmental control. Ecotype-food (i.e., genotype-by-environment) interactions were negligible. The directions of plastic and genetic effects were usually aligned. This suggests that life histories are mosaics with unequal rates of phenotypic and evolutionary change. Broadly speaking of "life-history evolution" masks a complex interplay of genes and environment on the multiple traits that underpin life-history strategies.

evolutionary biology↗

bioRxiv2021

Rapid genomic convergent evolution in experimental populations of Trinidadian guppies (Poecilia reticulata)

It is now accepted that phenotypic evolution can occur quickly but the genetic basis of rapid adaptation to natural environments is largely unknown in multicellular organisms. Population genomic studies of experimental populations of Trinidadian guppies (Poecilia reticulata) provide a unique opportunity to study this phenomenon. Guppy populations that were transplanted from high-predation (HP) to low-predation (LP) environments have been shown to mimic naturally-colonised LP populations phenotypically in as few as 8 generations. The new phenotypes persist in subsequent generations in lab environments, indicating their high heritability. Here, we compared whole genome variation in four populations recently introduced into LP sites along with the corresponding HP source population. We examined genome-wide patterns of genetic variation to estimate past demography, and uncovered signatures of selection with a combination of genome scans and a novel multivariate approach based on allele frequency change vectors. We were able to identify a limited number of candidate loci for convergent evolution across the genome. In particular, we found a region on chromosome 15 under strong selection in three of the four populations, with our multivariate approach revealing subtle parallel changes in allele frequency in all four populations across this region. Investigating patterns of genome-wide selection in this uniquely replicated experiment offers remarkable insight into the mechanisms underlying rapid adaptation, providing a basis for comparison with other species and populations experiencing rapidly changing environments. IMPACT STATEMENTThe genetic basis of rapid adaptation to new environments is largely unknown. Here we take advantage of a unique replicated experiment in the wild, where guppies from a high predation source were introduced into four low predation localities. Previous reports document census size fluctuations and rapid phenotypic evolution in these populations. We used genome-wide sequencing to understand past demography and selection. We detected clear signals of population growth and bottlenecks at the genome-wide level matching known census population data changes. We then identified candidate regions of selection across the genome, some of which were shared between populations. In particular, using a novel multivariate method, we identified parallel allele frequency change at a strong candidate locus for adaptation to low predation. These results and methods will be of use to those studying evolution at a recent, ecological timescale.

evolutionary biology↗

bioRxiv2021

Substantial intraspecific variation in energy budgets: biology or artefact?

O_LIDynamic energy budget (DEB) models provide a mechanistic description of life-histories in terms of fluxes of energy through biological processes. In these models, life-histories are a function of environmental conditions and of fundamental traits of the organism relating to the acquisition, allocation, and use of energy. C_LIO_LIThese traits are described by the parameters of the DEB model, which have been estimated for over 2500 species. Recent work has aimed to compare species on the basis of differences in DEB parameters. C_LIO_LIWe show that caution is required in such analyses, because (i) parameter estimates vary considerably as an artefact of the types of data used to fit the models, and (ii) there is substantial intraspecific variation in parameter values, reflecting biological differences among populations. C_LIO_LIWe show that similar patterns of growth and reproduction can be reproduced with very different parameter sets. Our results imply that direct comparison of DEB parameters across populations or species may be invalid. However, valid comparisons are possible if differences in the types of data used to fit the models are taken into account. C_LIO_LIWe estimated DEB parameters for 16 populations of Trinidadian guppy, identifying differences in resource allocation and metabolic rate consistent with evolved life-history differences among these populations. C_LIO_LIVariation in parameter values was substantial: if intraspecific variation in DEB parameters is greater than currently measured levels of interspecific variation, the detection of broad-scale patterns in energy budgets across species will be challenging. C_LI

evolutionary biology↗