Phylogenomic analyses show repeated evolution of hypertrophied lips among Lake Malawi cichlid fishes

Genetic relationships between and within some Malawian cichlid genera

Genetic relationships were examined for a total of 90 individuals of 90 species or species var. from 13 genera of Malawian cichlids based on the sequences of an amplified 991-bp fragment of the mtDNA control region (mtDNA-CR). In the network analysis, no exclusive clades were made by all the members of any genera in this study. However, congeneric clades were observed by genera Buccochromis, Copadichromis, Protomelas, and Sciaenochromis, whereas no congeneric clades were observed by genera Mylochromis, Nimbochromis, and Otopharynx. In non-mbuna, an Aulonocara-Lethrinops group was divided into two groups, and the mean genetic distance of the larger group was much lower from mbuna than from other non-mbuna. Overall mean genetic distance within a genus was generally low in mbuna, whereas it was relatively high in non-mbuna. In the genetic tree of each genus, two or more large clades were observed, and some clades, such as those of Aulonocara hansbaenschi and Aulonocara nyassae in genus Aulonocara, Lethrinops micrentodon and Lethrinops sp. "gold harbor" in Lethrinops, and Otopharynx ovatus and Otopharynx brooksi in Otopharynx, were very deeply differentiated. Besides, a mbuna species, Pseudotropheus crabro, was extremely deeply differentiated from other members of this genus. These results suggest a widespread morphological convergence across the taxa in parallel with deep genetic differentiation in the long evolutionary story and some possibility of generation of the species of Aulonocara-Lethrinops group by hybridization of small non-mbuna and mbuna species. Furthermore, taxonomical reexamination is necessary based on a strong support by genetic connection.

Multiple paths toward repeated phenotypic evolution in the spiny-leg adaptive radiation (Tetragnatha; Hawai'i)

The repeated evolution of phenotypes provides clear evidence for the role of natural selection in driving evolutionary change. However, the evolutionary origin of repeated phenotypes can be difficult to disentangle as it can arise from a combination of factors such as gene flow, shared ancestral polymorphisms or mutation. Here, we investigate the presence of these evolutionary processes in the Hawaiian spiny-leg Tetragnatha adaptive radiation, which includes four microhabitat-specialists or ecomorphs, with different body pigmentation and size (Green, Large Brown, Maroon, and Small Brown). We investigated the evolutionary history of this radiation using 76 newly generated low-coverage, whole-genome resequenced samples, along with phylogenetic and population genomic tools. Considering the Green ecomorph as the ancestral state, our results suggest that the Green ecomorph likely re-evolved once, the Large Brown and Maroon ecomorphs evolved twice and the Small Brown evolved three times. We found that the evolution of the Maroon and Small Brown ecomorphs likely involved ancestral hybridization events, while the Green and Large Brown ecomorphs likely evolved through novel mutations, despite a high rate of incomplete lineage sorting in the dataset. Our findings demonstrate that the repeated evolution of ecomorphs in the Hawaiian spiny-leg Tetragnatha is influenced by multiple evolutionary processes.

A new species of Lethrinops (Cichliformes: Cichlidae) from a Lake Malawi satellite lake, believed to be extinct in the wild

A new species of cichlid fish, Lethrinops chilingali is described from specimens collected from Lake Chilingali, near Nkhotakota, Malawi. It is assigned to the genus Lethrinops based on the form of the lower jaw dental arcade and by the absence of traits diagnostic of the phenotypically similar Ctenopharynx, Taeniolethrinops and Tramitichromis. It also lacks the enlarged cephalic lateral line canal pores found in species of Alticorpus and Aulonocara. The presence of a broken horizontal stripe on the flanks of females and immature/non-territorial males of Lethrinops chilingali distinguishes them from all congeners, including Lethrinops lethrinus, in which the stripe is typically continuous. Lethrinops chilingali also has a relatively shorter snout, shorter lachrymal bone and less ventrally positioned mouth than Lethrinops lethrinus. It appears likely that Lethrinops chilingali is now extinct in the wild, as this narrow endemic species has not been positively recorded in the natural environment since 2009. Breeding populations remain in captivity.

A new species of deep-water Lethrinops (Cichlidae) from Lake Malawi

A new species of cichlid fish, Lethrinops atrilabris is described from specimens collected by trawling at a depth of around 90 m off Monkey Bay, southern Lake Malawi. It is assigned to the genus Lethrinops on the basis of its vertical flank barring, lack of enlarged cephalic lateral line canal pores and the form of the lower jaw dental arcade. It can be distinguished from congeneric species by its male breeding dress of contrasting flank barring and dark ventral surface, most strikingly on the lips, throat and chest, its relatively small known maximum size [<75 mm standard length (SL)], large eyes (38%-41% head length), laterally compressed body (depth 2.5-2.7 times max head width) and lower gill raker count (13-14).