The Tetramerium lineage (Acanthaceae: Justicieae) does not support the Pleistocene Arc hypothesis for South American seasonally dry forests

Abstract

The South American genera Pachystachys, Schaueria, and Thyrsacanthus need to be recircumscribed. The congruence among biogeographical events found for the Tetramerium lineage suggests that the dry forest centers currently dispersed throughout South America are relatively old remnants, probably isolated since the Neogene, much earlier than the Last Glacial Maximum postulated by the Pleistocene Arc hypothesis. In addition to exploring the Pleistocene Arc hypothesis, this research also informs evolution in a lineage with numerous geographically restricted and threatened species.

Distributional patterns of Neotropical seasonally dry forest birds: a biogeographical regionalization

“…). This agrees with the idea of independent evolutionary histories among NSDF nuclei across their distribution (Becerra, ; Côrtes et al., ; de Melo et al., ).…”

“…In fact, Pennington et al (2009) andLinares-Palomino et al (2011) suggested that widespread species in NSDFs are an exception: only 1.43% of plant species are recorded in~50% of the floristic nuclei defined across the region. This paucity of widespread NSDF species argues strongly against a widespread Pleistocene NSDF formation throughout the Neotropics, rather suggesting dispersal limitation in NSDF biota and a mixed evolutionary history across their distribution, with ecological similarities arising from climatic convergence (Cracraft, 1985;Mayle, 2004;Becerra, 2005;Côrtes et al, 2015;Banda et al, 2016;de Melo et al, 2016).…”

Recircumscription and two new species of Pachystachys (Tetramerium lineage: Justicieae: Acanthaceae)

“…Schaueria azaleiflora Rusby, which also possesses narrow bracts, together with species of Streblacanthus , form a grade basal to Pachystachys (our Fig. , based on results from Côrtes et al ). These relationships suggest that narrow bracts are plesiomorphic in the clade.…”

“…For instance, although the type species of Streblacanthus, S. monospermus Kuntze, diverged near the root of the ‘ Tetramerium lineage’, the other three species of the genus form a grade near Pachystachys Nees (Daniel et al , our Fig. , based on results from Côrtes et al ).…”

“… Summary cladogram based on phylogenetic analysis of four plastid ( trnL–F, trnT–L, trnS–G, rpS16 ) and one nuclear (ITS) molecular markers (from Côrtes et al ), showing relevant relationships for the Pachystachys clade in Justicieae. Bold lines represent well‐supported clades (posterior probability 0.95–1.0 and bootstrap 90–100%); arrows show branches without support.…”