Interfamilial relationships in order Fabales: new insights from the nuclear regions sqd1 and 26S rDNA

Abstract

Leguminosae, Polygalaceae, Quillajaceae and Surianaceae together comprise the order Fabales.Phylogenetic relationships within Fabales remains an unsolved problem even though interfamilial relationships have been examined in a number of studies using different sampling approaches and both molecular and morphological data. In this study, we gather information from the nuclear 26S rDNA region as well as previously published data from the sqd1, matK and rbcL regions. Phylogenetic analyses were performed by maximum parsimony, maximum likelihood, and Bayesian inference.Overall, the best-supported topology for the relationships among families within the order places the pair of Leguminosae and Polygalaceae as sister to the pair of Quillajaceae and Surianaceae. However, our approximately unbiased (AU) test of the combined data results has shown that none of the seven different topologies rejected. Furthermore, three topologies were not significantly different from each other. Therefore, similar to the previous studies, this study did not find wellsupported dichotomous relationships among the four Fabales families. The Fabales topology was very sensitive to both data choice and the phylogenetic methods used, which may indicate a rapidnear-simultaneous evolution of the four Fabales families. Our results also show that while nuclear sqd1 can be helpful as a complementary region, both the nuclear sqd1 and rDNA 26S regions could be problematic when analysed individually.

Reconstructing an historical pollination syndrome: keel flowers

“…The divergence-time analysis was congruent with previous studies (e.g., [ 12 , 39 ]), with short internal branches of Fabales reflecting the rapid radiation already highlighted for this clade [ 12 , 48 , 49 ]. The divergence-time analysis also showed that keel flowers in crown Papilionoideae 67.19 Ma (95% HPD 62.5–64.9) evolved before the origin of Polygalaceae (63.59 Ma, 95% HPD 62.7–58.2 Ma) and tribe Polygaleae (45.16, 95% HPD 44.7–38.8 Ma), even if we accept Xanthophyllum as polymorphic in terms of the presence or absence of keel-flowers [ 50 ].…”

“…Similarly, the evolutionary origin of the six subfamilies of Fabaceae has been reported as near simultaneous [ 81 ]. While the current study exceeds the taxon sampling of Bello et al [ 12 , 17 ], Aygoren Uluer et al [ 49 ] and Koenen et al [ 81 , 82 ], it is the same as Aygoren Uluer et al [ 48 ]; however, none of these studies were able to support a robust topology for the order. Furthermore, Koenen et al’s [ 81 ] recently published phylogeny of the early evolving Leguminosae based on 1103 nuclear orthologues included only two Polygalaceae and one Surianaceae taxa, and therefore, it would not be possible to explore our molecular dating and ancestral reconstructions on their trees.…”

“…Whilst recent studies have employed considerable more sequence data (e.g., [ 80 – 82 ]), these data are not presently available across the Fabales. The monophylly of Fabales has been strongly supported; yet, both the fossil record and molecular studies (e.g., [ 12 , 17 , 48 , 49 ]) suggest a rapid radiation for the order, which causes unstable phylogenetic relationships among the four families, namely, change in the topology and the root of the order by the choice of genes, outgroups and phylogenetic methods. Similarly, the evolutionary origin of the six subfamilies of Fabaceae has been reported as near simultaneous [ 81 ].…”