Population genetics of the invasive cryptogenic anemone, Anemonia alicemartinae, along the southeastern Pacific coast

• We evaluated the spatial pattern of genetic diversity of the invasive anemone Anemonia alicemartinae
• We found no geographic structure and low genetic diversity using COI mtDNA sequences
• The well-documented 30°S biogeographical break is not a barrier to the invasive anemone
• Haplotype network configure supports recent population expansion
• Lack of genetic structure may be related to asexual reproduction and human transport mediated by maritime activities.

One of the most important issues in biological invasions is understanding the factors and mechanisms determining the invasion success of non-native species. Theoretical and empirical works have shown that genetic diversity is a determinant of invasion success; thus, studying spatial patterns of genetic diversity, and exploring how biological and physical factors shape this population trait, are fundamental for understanding this phenomenon. Coastal marine ecosystems are one of the most susceptible habitats to invasion given the complex network of maritime transport. In this work we study the cryptogenic anemone, Anemonia alicemartinae, which has rapidly increased its geographical range southward during the last 50 years (approx. 2000 km) along the southeastern Pacific coast. Based on COI mtDNA sequences we evaluated three main hypotheses: a) the genetic diversity of A. alicemartinae decreases according to the direction of invasion (from north to south); b) there is biogeographic–phylogeographic concordance at the 30°S biogeographic break; and c) the demographic history is coherent with a recent geographic expansion. A total of 161 individual samples of A. alicemartinae were collected along the southeastern Pacific coast range of distribution, covering more than 2000 km, including samples along the 30°S biogeographical break. Results showed low genetic diversity (Hd = 0.253; π = 0.08) and a lack of geographic population genetic structure (FST = − 0.009, p-value = 0.656). The highest genetic diversity was observed in Peru (Chero and Mesas) and at localities close to the main Chilean seaports. We did not observe concordance between biogeographic and phylogeographic patterns or isolation by distance. Demographic indices (D = − 2.604, p < 0.001; Fu's = − 26.619, p < 0.001), as well as a star-like configuration of the haplotype network support recent population expansion of this species. Our results, together with historical field observations, support the idea that the current distribution of A. alicemartinae may be explained by an increase in population size from one small ancestral population probably from the south of Peru, with subsequent human-mediated southward transport, probably associated with regional-scale maritime activities.

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