Baczenas, J. J. | Search bioRxiv

bioRxiv2022

Recurrent evolution of small body size and loss of the sword ornament in Northern Swordtail fish

Across the tree of life, species have repeatedly evolved similar phenotypes. While well-studied for ecological traits, there is also evidence for convergent evolution of sexually selected traits. Swordtail fish (Xiphophorus) are a classic model system for studying sexual selection, and female Xiphophorus exhibit strong mate preferences for large male body size and a range of sexually dimorphic ornaments. However, sexually selected traits have been lost multiple times in the genus. Phylogenetic relationships between species in this group have historically been controversial, likely as a result of prevalent gene flow, resulting in uncertainty over the number of losses of ornamentation and large body size. Here, we use whole-genome sequencing approaches to re-examine phylogenetic relationships within a Xiphophorus clade that varies in the presence and absence of sexually selected traits. Using wild-caught individuals, we determine the phylogenetic placement of a small, unornamented species, X. continens, confirming an additional loss of ornamentation and large body size in the clade. With these revised phylogenetic relationships, we analyze evidence for coevolution between body size and other sexually selected traits using a phylogenetically independent contrasts approach. These results provide insights into the evolutionary pressures driving the recurrent loss of suites of sexually selected traits.

evolutionary biology↗

bioRxiv2021

Zika virus infection of pregnant Ifnar1-/- mice triggers strain-specific differences in fetal outcomes

Zika virus (ZIKV) is a flavivirus that causes a constellation of adverse fetal outcomes collectively termed Congenital Zika Syndrome (CZS). However, not all pregnancies exposed to ZIKV result in an infant with apparent defects. During the 2015-2016 American outbreak of ZIKV, CZS rates varied by geographic location. The underlying mechanisms responsible for this heterogeneity in outcomes have not been well defined. Therefore, we sought to characterize and compare the pathogenic potential of multiple Asian/American-lineage ZIKV strains in an established Ifnar1-/- pregnant mouse model. Here, we show significant differences in the rate of fetal demise following maternal inoculation with ZIKV strains from Puerto Rico, Panama, Mexico, Brazil, and Cambodia. Rates of fetal demise broadly correlated with maternal viremia but were independent of fetus and placenta virus titer, indicating that additional underlying factors contribute to fetus outcome. Our results, in concert with those from other studies, suggest that subtle differences in ZIKV strains may have important phenotypic impacts. With ZIKV now endemic in the Americas, greater emphasis needs to be placed on elucidating and understanding the underlying mechanisms that contribute to fetal outcome. IMPORTANCEZika virus (ZIKV) actively circulates in 89 countries and territories around the globe. ZIKV infection during pregnancy is associated with adverse fetal outcomes including birth defects, microcephaly, neurological complications, and even spontaneous abortion. Rates of adverse fetal outcomes vary between regions, and not every pregnancy exposed to ZIKV results in birth defects. Not much is known about how or if the infecting ZIKV strain is linked to fetal outcomes. Our research provides evidence of phenotypic heterogeneity between Asian/American-lineage ZIKV strains and provides insight into the underlying causes of adverse fetal outcomes. Understanding ZIKV strain-dependent pathogenic potential during pregnancy and elucidating underlying causes of diverse clinical sequelae observed during human infections is critical to understanding ZIKV on a global scale.

microbiology↗