Reversão sexual em peixes Acanthomorpha: distribuição espacial e relacional entre as comunidades

Abstract

To think of sex and its associated phenotypic traits as something static, invariant, is an obsolete mentality and incoherent with the evolutionary scenarios that point to multiple origins and convergences of hermaphroditism and sexual reversal among vertebrates. Hermaphroditism is associated with genetic factors and responses to environmental and social stimuli, where phenotypic sexual expression occurs through synchronous or sequential pathways. Sex reversals are classified as protogynous, protandrous or bidirectional. Among vertebrates, the teleost fish (clade Actinopterygii) are the only group to present sex reversal as an evolutionary strategy with multiple independent origins and convergences. A more inclusive and diverse lineage within Teleostei is defined by the clade Acanthomorpha, who has the greatest diversity of sexual strategies, including the most complex sex reversal mechanisms among hermaphroditic fish. This study reviews the literature and explores the global spatial distribution of hermaphroditic bony fish allocated in the specious clade Acanthomorpha with synchronous or sequential sex reversals in marine and freshwater environments. The purpose was to compile information on hermaphroditic fish, their most frequent modes of sex reversal and their respective global geographic distributions to investigate general patterns of sexual evolution in vertebrates and the biogeographic regions that exert extraordinary influences on the structuring of hermaphrodite communities. A literature review was performated to obtain the necessary information about the hermaphroditic species in Acanthomorpha, including: the diversity of valid species, sex reversal strategies and geographic distributions in marine and freshwater biogeographic regions. All information collected was extracted from the literature by searching articles, books and museum catalogs. The geographic distributions of the species were inferred through datasets obtained from metadata repositories available online. In possession of such cleaned dataset, the spatial structuring of communities of hermaphrodite acanthomorphs was investigated using network theory with two different clustering algorithms. As a result, an extensive list was prepared with 223 hermaphroditic species, being 213 marine and 10 freshwater. Of these species, 26 are synchronous hermaphrodites and 197 are sequential hermaphrodites. Among sequential hermaphrodites, 151 are protogynous, 28 are protandrous, and 18 are serial bidirectional. Hermaphrodite acanthomorphs are widely distributed around the planet, occurring in all biogeographic realms, except Subarctic America. They are most diverse in tropic marine regions, with an extraordinary presence in shallow seas with coral reefs in the Indian Ocean (i.e., Indo-Malay and Australasian regions). There is a spatial structuring of hermaphroditic fish communities inhabiting different biogeographic realms, however the number of communities depends on the chosen algorithm. Common between the two algorithms is the existence of a community in the Americas and another distributed in the southern Eurasia, Central and Eastern Eurasia, Afrotropics, Indomalia and Oceania. The diversity of hermaphrodite acanthomorphs in Antarctica is low (e.g., 1 species), so there is no viable hypothesis on the spatial structuring in this region. Depending on the clustering algorithm, communities of hermaphroditic acanthomorphs of the Nordic seas, such as those present in the realms of Western Eurasia and Subarctic Eurasia, form independent communities or cluster with kingdoms located to the east of the planet.