Anthropogenic biological invasions represent major concerns but enable us to investigate rapid evolutionary changes and adaptation to novel environments. The goldfish Carassius auratus with sexual diploids and asexual triploids coexisting in natural waters, is one of the most widespread invasive fishes in Tibet, providing an ideal model to study evolutionary processes during invasion in different reproductive forms from the same vertebrate. Here, using whole-genome resequencing data of 151 C. auratus individuals from invasive and native ranges, we found different patterns of genomic responses between diploid and triploid populations during their invasion to Tibet. For diploids, although invasive individuals derived from two different genetically distinct sources and had a relative higher diversity (π) at the population level, their individual genetic diversity (genome-wide observed heterozygosity) was significantly lower (21.4%) than that of source individuals. Population structure analysis revealed that the invasive individuals formed a specific genetic cluster distinct from the source populations. Runs of homozygosity analysis showed low inbreeding only in invasive individuals, and only the invasive population experienced a recent decline in effective population size reflecting founder events. For triploids, however, invasive populations showed no loss of individual genetic diversity and no genetic differentiation relative to source populations. Regions of putative selective sweeps between invasive and source populations of diploids mainly involved genes associated with mannosidase activity and embryo development. Our results suggest invasive diploids deriving from distinct sources still lost individual genetic diversity resulting from recent inbreeding and founder events and selective sweeps, and invasive triploids experienced no genetic change owing to their reproduction mode of gynogenesis that precludes inbreeding and founder effects and may make them more powerful invaders.

Resource polymorphism is a ubiquitous phenomenon in vertebrates and may represent a critical intermediate stage in speciation. Freshwater lakes in high-altitude areas represent a natural system for understanding resource polymorphism in fishes in diverse lacustrine environments and a few co-distributed species. We report resource polymorphism in a cyprinid fish, Schizopygopsis thermalis, in Lake Amdo Tsonak Co, a headwater lake in the upper Salween River system. Two morphs, planktivorous and benthivorous, were identified according to geometric morphological and traditional linear traits. The planktivorous morph exhibits a longer head and lower jaw, larger asymptotic standard length (L∞), lower growth rate (k) and higher growth performance index (φ) than the benthivorous morph. With respect to descriptive traits, the planktivorous morph possesses a terminal mouth and a highly developed mucus cavity in the cheek and chin, while the benthivorous morph is characterized by an inferiorly positioned mouth with a sharpened horny edge on the lower jaw. Our results indicate that distinct pelagic-benthic resources and low interspecific competition in the lake drove the initial differentiation of the two morphs and that partial spatial reproductive isolation might maintain and reinforce the differences between them.