Phylogeny of the climber genus Haumania (Marantaceae) endemic to the tropical lowland rainforest in Central Africa

The genus Haumania (Marantaceae) consists of three described species of perennial climbers endemic to the tropical lowland rainforest in Central Africa. To unravel their phylogenetic relationship to each other, we used variation among DNA sequences of two nuclear ribosomal (nr) and four plastid (p) markers in five to seven accessions per species sampled across their respective distribution range. Maximum parsimony and Bayesian analyses were applied. All datasets and analyses corroborated the monophyly of the genus. Within the genus, individuals of the species H. danckelmaniana and H. leonardiana were each monophyletic. Individuals of H. liebrechtsiana, however, were paraphyletic. They clustered into two distinct geographic clades (Gabon and Democratic Republic of Congo), with the Gabonese clade being most closely related to the individuals of H. danckelmaniana. The latter might be due to introgression in areas of distributional overlap between these two species, as shown in earlier phylogeographic studies. A recent hybridisation event between H. danckelmaniana and H. liebrechtsiana is documented here in a single individual by incongruence in the nr and p dataset. Overall, the study provides support for H. leonardiana being sister to all other species of this genus. To confirm the absence of hybridisation in H. leonardiana further sampling is proposed in the respective areas of distributional overlap with its sister species.

Extensive Introgression among Ancestral mtDNA Lineages: Phylogenetic Relationships of the Utaka within the Lake Malawi Cichlid Flock

We present a comprehensive phylogenetic analysis of the Utaka, an informal taxonomic group of cichlid species from Lake Malawi. We analyse both nuclear and mtDNA data from five Utaka species representing two (Copadichromis and Mchenga) of the three genera within Utaka. Within three of the five analysed species we find two very divergent mtDNA lineages. These lineages are widespread and occur sympatrically in conspecific individuals in different areas throughout the lake. In a broader taxonomic context including representatives of the main groups within the Lake Malawi cichlid fauna, we find that one of these lineages clusters within the non-Mbuna mtDNA clade, while the other forms a separate clade stemming from the base of the Malawian cichlid radiation. This second mtDNA lineage was only found in Utaka individuals, mostly within Copadichromis sp. “virginalis kajose” specimens. The nuclear genes analysed, on the other hand, did not show traces of divergence within each species. We suggest that the discrepancy between the mtDNA and the nuclear DNA signatures is best explained by a past hybridisation event by which the mtDNA of another species introgressed into the ancestral Copadichromis sp. “virginalis kajose” gene pool.

From Dampier to DNA: the 300-year-old mystery of the identity and proposed allopolyploid origin of Conostylis stylidioides (Haemodoraceae)

The tetraploid Conostylis stylidioides (n= 16) has been proposed to be a stabilised hybrid between the diploid (n = 8) species C. prolifera and C. candicans because of morphological and geographical intermediacy, as well as a polyploid chromosome number. To test this hybrid-origin hypothesis, we used the DNA-fingerprinting technique amplified fragment length polymorphism (AFLP) and measured genetic variation within these taxa, as well as the putative outgroups C. robusta and C. aculeata. One AFLP primer pair generated 192 dominant markers for 36 samples from these species, of which 189 were polymorphic. Polymorphism within populations was uniformly high for all species, with 66–86% of all fragments polymorphic and estimates of heterozygosity ranging from 0.36 to 0.41. Ordination, UPGMA and maximum parsimony analyses of these genetic data consistently clustered species, supporting the current species’ level taxonomy. The intermediate placement of C. stylidioides between C. proliferaand C. candicans on the maximum parsimony tree supports the hybrid-origin hypothesis, although other interpretations are possible. The phenetic results for AFLP data, in which C. stylidioides is not strictly intermediate between C. prolifera and C. candicans, are either concordant with recent research suggesting that rapid intra- and inter-genomic rearrangements occur with the origin of polyploid taxa, or indicate an ancient hybridisation event. While our results do not reject the hybrid origin hypothesis, the extremely high levels of genetic variation detected with AFLP within these populations, in combination with extensive genomic reorganisation with the origin of C. stylidioides and the possibility of independent origins for different populations, make it difficult to confidently exclude other scenarios.