Hidden diversity—Delimitation of cryptic species and phylogeography of the cyprinid Garra species complex in Northern Oman

Cryptic diversity within two widespread diadromous freshwater fishes (Teleostei: Galaxiidae)

Identification of taxonomically cryptic species is essential for the effective conservation of biodiversity. Freshwater-limited organisms tend to be genetically isolated by drainage boundaries, and thus may be expected to show substantial cryptic phylogenetic and taxonomic diversity. By comparison, populations of diadromous taxa, that migrate between freshwater and marine environments, are expected to show less genetic differentiation. Here we test for cryptic diversity in Australasian populations (both diadromous and non-diadromous) of two widespread Southern Hemisphere fish species, Galaxias brevipinnis and Galaxias maculatus. Both mtDNA and nuclear markers reveal putative cryptic species within these taxa. The substantial diversity detected within G. brevipinnis may be explained by its strong climbing ability which allows it to form isolated inland populations. In island populations, G. brevipinnis similarly show deeper genetic divergence than those of G. maculatus, which may be explained by the greater abundance of G. maculatus larvae in the sea allowing more ongoing dispersal. Our study highlights that even widespread, 'high-dispersal' species can harbour substantial cryptic diversity and therefore warrant increased taxonomic and conservation attention.

Inland fishes of the Arabian Peninsula: Review and a revised checklist

The Arabian Peninsula comprises the seven countries of Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, the United Arab Emirates, and Yemen (including the Socotra archipelago), covering an area of more than 3 million km). Although arid habitats cover most parts of the Arabian Peninsula, the region has several freshwater systems and comprises all or parts of four freshwater ecoregions basins that support a variety of inland aquatics including fishes. The current checklist provides all fish species in inland waters of the Arabian Peninsula including all recognized and named taxa, documenting recent changes and controversies in nomenclature, records, taxonomic status, occurrence, synonyms, common English name, range distribution, and conservation status based on several field surveys throughout the area and available articles. The confirmed inland ichthyodiversity of the Arabian Peninsula comprise 48 species belonging to 25 genera, 14 families, nine orders, and a class. Among these, 10 species (20.8%) are alien, and 21 species (52.3%) are considered endemic to the Arabian Peninsula. Favonigobius reichei is a new record for inland waters of the Arabian Peninsula. The most diverse order is Cypriniformes (19 species, 39.6%), followed by Cyprinodontiformes and Gobiiformes (eight species, 16.7% in each), Cichliformes (four species, 8.33%), Mugiliformes (three species, 6.25%), Anguilliformes and Siluriformes (two species, 4.17% in each), and Centrarchiformes and Gonorynchiformes (one species, 4.2% each). Saudi Arabia and Oman with 23 species (47.9% each) rank first in fish diversity (both native and exotic), followed by Yemen (15 species, 31.25%), UAE (seven species, 14.58%), Bahrain (two species, 4.17%), and Qatar and Kuwait (one species, 2.1% each). Of 21 endemic species of the Arabian Peninsula, six, six, and four species are restricted to the territories of Oman, Saudi Arabia and Yemen, respectively. No endemic fish have been reported from Bahrain, Kuwait, Qatar, and the United Arab Emirates. The list also includes two subterranean species belonging to the genus Garra. The provided data will be necessary to take action for effective conservation management strategies and policies.

Rapid adaptive radiation in a hillstream cyprinid fish in the East African White Nile River basin

Adaptive radiation of freshwater fishes was long thought to be possible only in lacustrine environments. Recently, several studies have shown that riverine and stream environments also provide the ecological opportunity for adaptive radiation. In this study, we report on a riverine adaptive radiation of six ecomorphs of cyprinid hillstream fishes of the genus Garra in a river located in the Ethiopian Highlands in East Africa. Garra are predominantly highly specialized algae-scrapers with a wide distribution ranging from Southeast Asia to West Africa. However, adaptive phenotypic diversification in mouth type, sucking disc morphology, gut length and body shape have probably been found among these ecomorphs in a single Ethiopian river. Moreover, we found two novel phenotypes of Garra ("thick-lipped" and "predatory") that had not been discovered before in this species-rich genus (>160 species). Mitochondrial and genome-wide data suggest monophyletic, intrabasin evolution of Garra phenotypic diversity with signatures of gene flow from other local populations. Although sympatric ecomorphs are genetically distinct and can be considered to being young species as suggested by genome-wide single nucleotide polymorphism data, mitochondrial DNA was unable to identify any genetic structure suggesting recent and rapid speciation events. Some data suggest a hybrid origin of the novel "thick-lipped" ecomorph. Here we highlight how, driven by ecological opportunity, an ancestral trophically highly specialized lineage is likely to have rapidly radiated in a riverine environment promoted by the evolution of novel feeding strategies.