Severe fever with thrombocytopenia syndrome virus (SFTSV) is spreading rapidly in Asia. This virus is transmitted by the Asian longhorned tick ( Haemaphysalis longicornis ), which has parthenogenetically and sexually reproducing populations. Parthenogenetic populations were found in ≥15 provinces in China and strongly correlated with the distribution of severe fever with thrombocytopenia syndrome cases. However, distribution of these cases was poorly correlated with the distribution of populations of bisexual ticks. Phylogeographic analysis suggested that the parthenogenetic population spread much faster than bisexual population because colonization is independent of sexual reproduction. A higher proportion of parthenogenetic ticks was collected from migratory birds captured at an SFTSV-endemic area, implicating the contribution to the long-range movement of these ticks in China. The SFTSV susceptibility of parthenogenetic females was similar to that of bisexual females under laboratory conditions. These results suggest that parthenogenetic Asian longhorned ticks, probably transported by migratory birds, play a major role in the rapid spread of SFTSV.

Ecosystem regime shifts attract a growing concern because irreversible nonlinear, abrupt changes can significantly alter the services that the ecosystem offers to human society. Regime shifts between contrasting alternative states occur when environmental conditions cross a specific threshold, with ecological resilience decreasing as the system approaches the tipping point (Ma et al., 2021). Therefore, measuring and quantifying ecological resilience is critical to improving ecosystem management and conservation. Previous assessments of ecological resilience often focused on identifying thresholds or early warning indicators based on critical slowing down (Contamin & Ellison, 2009;Dakos et al., 2015). However, these methods do not include the specific mechanisms of regime shifts. Positive feedback is the key to understanding the pattern of ecosystem response to environmental changes, with high feedback strength creating

Severe fever with thrombocytopenia syndrome virus (SFTSV) is spreading rapidly in Asia. It is transmitted by Haemaphysalis longicornis (Asian longhorned tick, ALT), which has both parthenogenetically and sexually reproducing populations. Parthenogenetic populations were found in at least 15 provinces in China and strongly correlated with the distribution of SFTS. The distribution of SFTS cases was however poorly correlated with the distribution of populations of bisexual ALTs. Phylogeographic analysis suggested that the parthenogenetic population spread much faster than bisexual population because colonization is independent of sexual reproduction. A higher proportion of parthenogenetic ALTs were collected from migratory birds captured at an SFTS endemic area, implicating the contribution to the long-range movement of ALTs in China. The SFTSV susceptibility of parthenogenetic females was like that of bisexual females under laboratory conditions. These results suggest that parthenogenetic ALT, probably transported by migratory birds, play a major role in the rapid spread of SFTSV.

Although population density and body mass are known to alter the mating strategies of individuals, their impacts on reproductive success have not been fully investigated. We examined genetic mating system variation (estimated number of mating partners), reproductive success (offspring number), and sperm competition intensity (sires per litter) in semi-natural populations of Brandt’s voles (Lasiopodomys brandtii) under low-, medium- and high-densities. We used 12 microsatellite genetic markers and parentage assignment of 3516 voles, with the aim of identifying the estimated number of mating partners and offspring produced by founder individuals. We provided strong evidence that individuals with more mating partners experienced increased reproductive success in all density groups, as measured by the production of more offspring, compared with individuals that had fewer mating partners. Further, we found that large males had more mating partners (especially in high-population density enclosures) and also produced more offspring relative to smaller males. In high-density (HD) enclosures, the average reproductive success per female vole was lower (a negative density-dependent effect), but voles had more mating partners, more sires per litter, but lower paternity skew compared to low-density enclosures. Our results suggests that Brandt’s voles increased reproductive success through increasing mating partners under HD stress which may have significant implications in offsetting the negative density-dependency effect on population growth.