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The costs of mischoosing are not uniform across individuals


Matching habitat choice is a particular form of habitat selection based on self?assessment of local performance that offers individuals a means to optimize the match of phenotype to the environment. Despite the advantages of this mechanism in terms of increased local adaptation, examples from natural populations are extremely rare. One possible reason for the apparent rarity of matching habitat choice is that it might be manifest only in those segments of a population for which the cost of a phenotype–environment mismatch is high. To test this hypothesis, we used a breeding population of sockeye salmon (Oncorhynchus nerka) exposed to size-dependent predation risk by bears, and evaluated the costs of mischoosing in discrete groups (e.g. male versus females, and ocean?age 2 versus ocean?age 3) using reproductive life span as a measure of individual performance. Bear preference for larger fish, especially in shallow water, translates into a performance trade-off that sockeye salmon can potentially use to guide their settlement decisions. Consistent with matching habitat choice, we found that salmon of similar ocean?age and size tended to cluster together in sites of similar water depth. However, matching habitat choice was only favoured in 3?ocean females – the segment of the population most vulnerable to bear predation. This study illustrates the unequal relevance of matching habitat choice to different segments of a population, and suggests that ‘partial matching habitat choice' could have resulted in an underestimation of the actual prevalence of this mechanism in nature. informacion[at] Camacho & Hendry (2020) Matching habitat choice: it's not for everyone. Oikos DOI 10.1111/oik.06932
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Fish eggs can be dispersed by waterfowl

Fish eggs can be dispersed by waterfowl

Researchers have found that eggs of two fish species can survive passage through the digestive tract of waterfowl after being swallowed, and this finding may help explain the long-standing mystery of how some species of fish colonize isolated lakes and ponds. After finding eggs in the droppings of the Coscoroba swan collected on the banks of Brazilian lakes, the researchers decided to test whether eggs of two annual fish species (the killifish Austrolebias minuano and Cynopoecilus fulgens) remained viable even after they have been ingested by birds and expelled in their feces. The researchers mixed 650 fish eggs into the food of a captive coscoroba swan. Five live fish eggs were recovered from the faeces, which continued their development and were able to successfully hatch. The live eggs had survived as long as 30 h inside the guts of the swan. The results show the possibility that fish eggs can be transported in the digestive tract of migratory birds, which regularly fly between lakes and other wetlands. This is the first scientific study to demonstrate this, although scientists have long wondered how fish manage to colonize remote places and have speculated that birds may be able to carry fish eggs stuck to their feet, beaks or feathers. This new discovery helps to resolve a historical debate held since the XIX century by naturalists. The eggs of killifish may be uniquely resistant as they can often survive long periods of drought in the mud of dried-out ponds. It remains to be seen in future studies if other kinds of fish also have this amazing ability to move as eggs inside waterbirds. informacion[at] Silva et al (2019) Killfish eggs can disperse via gut passage through waterfowl. Ecology