Gante, H. F. | bioRxiv Science

bioRxiv2022

Effects of haemosporidian co-infection and parasitemia on reproductive strategies in a polymorphic species

Host-parasite interactions play a significant role in evolution. Parasite infections impose fitness costs that can trigger trade-off responses in host reproductive strategies. Individuals can invest limited resources in parasite defense, such as stimulating the immune system, or perform terminal reproductive investment. Here, we investigated how haemosporidian co-infection and parasitemia influence different reproductive strategies in a polymorphic bird species (the white-throated sparrow, Zonotrichia albicollis). We provided an account of the impacts of co-infection and parasitemia on host reproductive success and reproductive strategies in response to parasite infection. We tested the effect of co-infection and parasitemia on reproductive success (fledgling number, extra-pair paternity, ratio social/genetic offspring) and the effect of parental infection on nestling quality (mean nestling growth rate and body condition). We found that co-infection increases reproductive extra-pair paternity and nestling mean body condition. Parental high parasitemia positively impacts the ratio of genetic offspring belonging to the social father and has mixed results on nestling quality. We observed that co-infection in females and parasitemia in males might trigger a switch in reproductive strategy towards a terminal investment for co-infected individuals. In contrast, high parasitemia in females negatively impacted their offspring fitness, possibly due to the reallocation of resources for fighting the infection.

ecology↗

bioRxiv2022

Widespread hybridization between invasive bleak (Alburnus alburnus) and native Iberian chubs (Squalius spp.): a neglected threat

Hybridization between native and exotic species is a major conservation issue. In Iberian rivers, which are simultaneously among the most invaded and diverse ecosystems, harboring a high proportion of endemic fishes, this issue is becoming highly concerning. To date, hybridization has been reported to occur between the invasive bleak Alburnus alburnus and the endemic chubs Squalius alburnoides and S. pyrenaicus, in some scattered locations. However, the bleak is increasingly spreading in the region, potentially increasing the risks of hybridization with these and other Squalius species. To gather a more comprehensive picture on the current extension of hybridization, we compiled and mapped records on hybrids between bleak and chubs collected by multiple research teams in different ongoing projects in the Portuguese territory, and genetically assessed the hybrid identity of specimens in an area of sympatry between bleak and S. carolitertii, using nuclear and mitochondrial markers. We found that hybridization with bleak is widespread in several Portuguese river basins and involves at least three endemic chubs, S. alburnoides, S. pyrenaicus and S. carolitertii. This may have serious consequences, including not only waste of reproductive effort and damage of genetic integrity, but also putative shifts on the reproductive dynamics of the Squalius system, which includes endemic hybrids, reproducing sexually and nonsexually. Hybridization should be recognized as a significant impact of biological invasions, and we recommend that future studies should characterize the fitness of hybrids and their ecological and genetic interactions with parental Iberian fish, to elucidate effective conservation measures.

zoology↗