| 1. |
- Sánchez-Guillén, Rosa A., et al.
(författare)
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The evolutionary history of colour polymorphism in Ischnura damselflies
- 2018
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Ingår i: Journal of evolutionary biology. - 1010-061X.
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Tidskriftsartikel (refereegranskat)abstract
- A major challenge in evolutionary biology consists of understanding how genetic and phenotypic variation is created and maintained. In this study, we investigated the origin(s) and evolutionary patterns of the female-limited colour polymorphism in ischnuran damselflies. These consist of the presence of one to three colour morphs: one androchrome morph with a coloration that is similar to the male and two gynochrome morphs (infuscans and aurantiaca) with female-specific coloration. We (i) documented the colour and mating system of 44 of the 75 taxa within the genus Ischnura, (ii) reconstructed the evolutionary history of colour and mating system to identify the ancestral state, (iii) evaluated the stability of the colour morph status over time and (iv) tested for a correlation between colour and mating system. We found that the ancestral female colour of Ischnura was monomorphic and aurantiaca and that colour morph status changed over time, characterized by many gains and losses across the species tree. Our results further showed that colour polymorphism is significantly more frequent among polyandric species, whereas monandric species tend to be monomorphic. Research on some Ischnura species has shown that colour morphs have evolved to reduce male mating harassment, and our finding that the same phenotypic morphs have evolved multiple times (convergent evolution) suggests that several species in this genus might be experiencing similar selective pressures.
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| 2. |
- Svensson, Erik I., et al.
(författare)
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Frequency Dependence and Ecological Drift Shape Coexistence of Species with Similar Niches
- 2018
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Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 191:6, s. 691-703
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Tidskriftsartikel (refereegranskat)abstract
- The coexistence of ecologically similar species might be counteracted by ecological drift and demographic stochasticity, both of which erode local diversity. With niche differentiation, species can be maintained through performance trade-offs between environments, but trade-offs are difficult to invoke for species with similar ecological niches. Such similar species might then go locally extinct due to stochastic ecological drift, but there is little empirical evidence for such processes. Previous studies have relied on biogeographical surveys and inferred process from pattern, while experimental field investigations of ecological drift are rare. Mechanisms preserving local species diversity, such as frequency dependence (e.g., rare-species advantages), can oppose local ecological drift, but the combined effects of ecological drift and such counteracting forces have seldom been investigated. Here, we investigate mechanisms between coexistence of ecologically similar but strongly sexually differentiated damselfly species (Calopteryx virgo and Calopteryx splendens). Combining field surveys, behavioral observations, experimental manipulations of species frequencies and densities, and simulation modeling, we demonstrate that species coexistence is shaped by the opposing forces of ecological drift and negative frequency dependence (rare-species advantage), generated by interference competition. Stochastic and deterministic processes therefore jointly shape coexistence. The role of negative frequency dependence in delaying the loss of ecologically similar species, such as those formed by sexual selection, should therefore be considered in community assembly, macroecology, macroevolution, and biogeography.
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