One of the most puzzling issues in phylogenetics and systematics is the reconstruction of interspecific relationships between entities extremely similar from a molecular point of view; this affinity is not always associated to a morphological resemblance. We faced this problem in the investigation of phylogenetic history of the genus Asperula L. (Rubiaceae) sect. Cynanchicae (DC.) Boiss.; for many members of the section, interspecific differentiation is truly subtle and discrimination is too often founded on obscure quantitative traits. Moreover, a hybrid and/or introgressive nature of some entities is suspected (e. g., Bernardoet al., 2010). Phylogenetic analysis was conducted mainly in a Bayesian framework (Ronquist & Huelsenbeck, 2003), which gave a higher supports for several clades, but methods based on maximum parsimony and maximum likelihood were also used. Basically, first outcomes indicate a global weak resolution of the relationships (i.e., various clades are collapsed or barely resolved). Unsurprisingly, clades including taxa with distinctive morphological traits (e. g., various Russian and some Greek taxa) exhibit a satisfactory resolution. A possible explanation for this low molecular variability could be sought in the relatively recent divergence of some entities; however, the presence of various autapomorphies in some terminal taxa may even suggest the opposite. An additional interpretation, especially in conditions of sympatry, would be the occurrence of hybridization and introgression. Apart from the necessity to find discriminating markers which may lead to a more resolved (and robust) phylogenetic hypothesis, we started to develop a microsatellite library to investigate the most difficult cases, in terms of low interspecific variability (Yaoet al., 2008). In these cases, we will be going to compare the interspecific differentiation with the pattern of variations between populations of the same speci es, in the effort to reach a phylogeographic hypothesis.
Phylogeny of Asperula L. sect. Cynanchicae (DC.) Boiss.: a starting effort / Gargiulo, Roberta; Del Guacchio, E.; DE CASTRO, Olga; Caputo, Paolo. - 5:(2013), pp. 26-26. (Intervento presentato al convegno 5th Congress ITALIAN SOCIETY FOR EVOLUTIONARY BIOLOGY tenutosi a Trento nel 28-31 Agosto).
Phylogeny of Asperula L. sect. Cynanchicae (DC.) Boiss.: a starting effort
GARGIULO, ROBERTA;Del Guacchio E.;DE CASTRO, OLGA;CAPUTO, PAOLO
2013
Abstract
One of the most puzzling issues in phylogenetics and systematics is the reconstruction of interspecific relationships between entities extremely similar from a molecular point of view; this affinity is not always associated to a morphological resemblance. We faced this problem in the investigation of phylogenetic history of the genus Asperula L. (Rubiaceae) sect. Cynanchicae (DC.) Boiss.; for many members of the section, interspecific differentiation is truly subtle and discrimination is too often founded on obscure quantitative traits. Moreover, a hybrid and/or introgressive nature of some entities is suspected (e. g., Bernardoet al., 2010). Phylogenetic analysis was conducted mainly in a Bayesian framework (Ronquist & Huelsenbeck, 2003), which gave a higher supports for several clades, but methods based on maximum parsimony and maximum likelihood were also used. Basically, first outcomes indicate a global weak resolution of the relationships (i.e., various clades are collapsed or barely resolved). Unsurprisingly, clades including taxa with distinctive morphological traits (e. g., various Russian and some Greek taxa) exhibit a satisfactory resolution. A possible explanation for this low molecular variability could be sought in the relatively recent divergence of some entities; however, the presence of various autapomorphies in some terminal taxa may even suggest the opposite. An additional interpretation, especially in conditions of sympatry, would be the occurrence of hybridization and introgression. Apart from the necessity to find discriminating markers which may lead to a more resolved (and robust) phylogenetic hypothesis, we started to develop a microsatellite library to investigate the most difficult cases, in terms of low interspecific variability (Yaoet al., 2008). In these cases, we will be going to compare the interspecific differentiation with the pattern of variations between populations of the same speci es, in the effort to reach a phylogeographic hypothesis.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
