Assortative mating – correlation between male and female traits – is common within populations and has the potential to promote genetic diversity and in some cases speciation. Despite its importance, few studies have sought to explain variation in the extent of assortativeness across populations. Here, we measure assortative mating based on an ecologically important trait, diet as inferred from stable isotopes, in 16 unmanipulated lake populations of three-spine stickleback. As predicted, we find a tendency toward positive assortment on the littoral–pelagic axis, although the magnitude is consistently weak. These populations vary relatively little in the strength of assortativeness, and what variation occurs is not explained by hypothesized drivers including habitat cosegregation, the potential for disruptive selection, costs to choosiness, and the strength of the relationship between diet and body size. Our results support recent findings that most assortative mating is positive, while suggesting that new approaches may be required to identify the environmental variables that drive the evolution of nonrandom mating within populations.
As climate change continues, anticipating species' responses to rising temperatures, requires an understanding of the relationship between metabolic rate and thermal sensitivity, which itself may vary over space and time. We measured metabolic rates of three representative marine invertebrate species (hermit crabs Pagurus hirsutiusculus, periwinkle snails Littorina sitkana, and mussels Mytilus trossulus) and evaluated the relationship between thermal sensitivity (Q 10 ) and thermal history. We tested the hypothesis that thermal history drives thermal sensitivity and quanti ed how this relationship differs over time (short-term to seasonal time scales) and between species. Organisms were collected from tide pools in Sitka, Alaska where we also recorded temperatures to characterize thermal history prior to metabolic rate assays. Using respirometry, we estimated mass-speci c oxygen consumption (MO 2 ) at ambient and increased temperatures for one individual per species per tide pool across three seasons. We evaluated relationships between thermal sensitivity and pool temperatures for time periods ranging from 1 day to 3 months prior to collection. For all species, thermal sensitivity was related to thermal history for the shorter time periods (1 day to 1 week). However, the direction of the relationships and most important thermal parameters (i.e., maximum, mean, or range) differed between species and seasons. We found that on average, P. hirsutiusculus and L. sitkana were more thermally sensitive than M. trossulus. These ndings show that variability in thermal history over small spatial scales in uences individuals' metabolic response to warming and may be indicative of these species' ability to acclimate to future climate change.
As climate change continues, anticipating species’ responses to rising temperatures, requires an understanding of the relationship between metabolic rate and thermal sensitivity, which itself may vary over space and time. We measured metabolic rates of three representative marine invertebrate species (hermit crabs Pagurus hirsutiusculus, periwinkle snails Littorina sitkana, and mussels Mytilus trossulus) and evaluated the relationship between thermal sensitivity (Q10) and thermal history. We tested the hypothesis that thermal history drives thermal sensitivity and quantified how this relationship differs over time (short-term to seasonal time scales) and between species. Organisms were collected from tide pools in Sitka, Alaska where we also recorded temperatures to characterize thermal history prior to metabolic rate assays. Using respirometry, we estimated mass-specific oxygen consumption (MO2) at ambient and increased temperatures for one individual per species per tide pool across three seasons. We evaluated relationships between thermal sensitivity and pool temperatures for time periods ranging from 1 day to 3 months prior to collection. For all species, thermal sensitivity was related to thermal history for the shorter time periods (1 day to 1 week). However, the direction of the relationships and most important thermal parameters (i.e., maximum, mean, or range) differed between species and seasons. We found that on average, P. hirsutiusculus and L. sitkana were more thermally sensitive than M. trossulus. These findings show that variability in thermal history over small spatial scales influences individuals’ metabolic response to warming and may be indicative of these species’ ability to acclimate to future climate change.
In many animal species, alternative reproductive tactics can result in alloparenting: adult individuals providing care for juveniles that are not genetically their own progeny. In species with parental care, males may exhibit “sneaking” behavior and fertilize eggs in the nest of another male, or nesting males may commit egg theft from a more successful male, possibly to help attract females. Alloparenting may have important consequences for both male and female reproductive output and mate choice, but rates of such non-paternity in natural populations are poorly understood in many taxa, as are the ecological factors that might influence these rates. Here, we quantified the frequency of non-paternity between males and the eggs in their nests within 15 natural populations of Threespine Stickleback, and tested whether the frequency of mismatch was predicted by characteristics of the lake (lake size and nest density) or features of individual males (body size and diet) or their chosen nest location (depth and presence of vegetation). The frequency of non-paternity was relatively high across all lakes (23–66%) but was not explained by lake-level characteristics (lake area or nest density). Alloparenting was more likely for individual males with more benthic diets (as measured by stable isotopes) and for males whose nests were closer to vegetation, although this effect varied across lakes. Our results suggest that individual-level characteristics of the male and nest influence the frequency of alloparenting, and that variation among individuals and populations should be considered in studies of the genetics and evolutionary consequences of alternative reproductive tactics.
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