Daphnia galeata and D. dentifera are geographically and ecologically separated whereas their hybrids occur in intermediate habitats: A survey of 44 Chinese lakes

Abstract

The idea that hybridization promotes range expansion has received recent attention, but support from field studies is limited. We hypothesized that in the cladoceran waterflea genus Daphnia, parental species are geographically and ecologically separated, whereas hybrids occupy intermediate or occasionally extreme environments, potentially facilitating range expansion of parental species. We assessed the distribution of Daphnia dentifera, Daphnia galeata and their interspecific hybrids across 44 lakes in China (using mitochondrial and microsatellite markers), and related it to geographical and environmental lake descriptors. Parental species were geographically separated: D. dentifera occurred in western and central China, and D. galeata in eastern and central China, whereas hybrids were found in the western and central parts of the country. However, after controlling for geographical differences, the effect of environment on species distribution was strong and significant. Specifically, D. dentifera was present in high‐altitude oligotrophic lakes, D. galeata in low‐altitude eutrophic lakes and hybrids at intermediate to high altitudes, mainly in mesotrophic lakes. Microsatellite data indicated that hybrids were locally produced rather than having migrated from elsewhere; they probably resulted from encounters between expanding D. galeata and resident D. dentifera. The present study provides evidence that hybrids can survive in habitats that are otherwise suitable for only one of their parental species, emphasizing the importance of hybridization in expansion of species gene pools.

Clonal diversity and substantial genetic divergence of the Daphnia similis species complex in Chinese lakes: Possible adaptations to the uplift of the Qinghai‐Tibetan Plateau

“…Based on two independent statistical approaches (i.e., FCA and STRUCTURE), there is obvious divergence between D. similis and D. sinensis populations, and a geographical separation of D. sinensis populations originating from two different regions, Eastern (Eastern Plain) and Western (the Qinghai-Tibetan Plateau) China. The ecological separation of two species from the D. similis species complex described here is consistent with previous studies for the D. longispina species complex: D. dentifera has been observed in high-altitude oligotrophic lakes in China, Japan, and Tajikistan (Ishida et al 2011;Möst et al 2013;Ma et al 2019a), whereas D. galeata is a common inhabitant of lower altitude, warmer and meso-or eutrophic habitats in China, Japan, and Europe (Keller et al 2008;Ishida et al 2011;Ma et al 2019a). The ecological separation of Daphnia species could be due to specific food requirements (Spaak et al 2012), or the abundance of predators in the studied lakes (Duffy et al 2004).…”

“…Previous studies of biodiversity and biogeography in the region have focused on aquatic vertebrates (e.g., Zhao et al ; Ding et al ) and terrestrial invertebrates (Zhao and Li ). Very few studies have focused on the biogeography and genetic diversity of aquatic invertebrate zooplankton from the Qinghai‐Tibetan Plateau (Xu et al ; Ma et al , b ).…”

“…Microsatellites are powerful molecular markers for tracing clonal lineages and exploring population structure, especially for Daphnia (e.g., Thielsch et al ; Yin et al ; Walser and Haag ; So et al ; Ma et al ). Thielsch et al () used microsatellites to explore the genetic structure of European D. longispina species complex populations.…”

Temperature and host diet jointly influence the outcome of infection in a Daphnia‐fungal parasite system

“…Two genotypes of Daphnia longispina × galeata hybrids (AMME_12 and AMME_51) were selected randomly from a wider collection of clonal lines isolated from Ammersee, Germany. Hybrids belonging to the D. longispina species complex are common and sometimes dominant inhabitants of permanent water bodies across the world (Griebel et al, ; Keller, Wolinska, Manca, & Spaak, ), being also able to colonise intermediate habitats that are not shared by their respective progenitor species (Ma, Hu, Smilauer, Yin, & Wolinska, ). Daphnia were maintained in synthetic culture medium (Saebelfeld, Minguez, Griebel, Gessner, & Wolinska, ) at 19°C, under a 12:12 light‐dark photoperiod and fed three times per week with 1 mg C/L of green alga S. obliquus.…”

Temperature increase altered Daphnia community structure in artificially heated lakes: a potential scenario for a warmer future

“…D. galeata is found in warmer lakes of the southern Alps, and those authors specifically identified temperature as the factor that explained the dominance of D. galeata in those habitats. In China, D. galeata is present at low altitudes, and absent from intermediate-or high-altitude lakes, although hybrids of this species can survive in higher-altitude (and thus colder) lakes 34 . Additionally, it has been reported that warm, iceless winters promote the population growth of D. galeata and D. galeata × D. longispina hybrids over that of pure D. longispina, whereas after harsh winters D. longispina gains an advantage 29 .…”