A new cryptic species in a new cryptic genus in the Caesalpinia group (Leguminosae) from the seasonally dry inter‐Andean valleys of South America

Abstract

The generic affiliation of the Andean species Caesalpinia trichocarpa, C. mimosifolia, and their close relatives has remained uncertain in all recent studies of Caesalpinia s.l. (Leguminosae, subfamily Caesalpinioideae). A new densely sampled phylogeny based on four DNA sequence regions (rps16, trn D‐trnT, ycf6‐ psbM, ITS) strongly supports the monophyly of an Andean clade. We propose that despite the lack of obvious diagnostic morphological synapomorphies, this Andean group should be considered as a distinct genus, here described as the new genus Arquita. Phylogenetic analyses also suggest a problem with species delimitation in this group. Within C. trichocarpa, accessions from disjunct geographic areas in Argentina, Bolivia and Peru each form a robustly supported, unresolved clade that includes C. mimosifolia. The morphological and genetic cohesiveness of the C. trichocarpa complex is investigated using morphometric phenetic analyses of qualitative and quantitative flower and leaf traits, and reconstruction of a densely sampled phylogeny using three plastid and one nuclear ribosomal DNA sequence loci. Our results suggest that the most geographically isolated of these clades, narrowly endemic to two inter‐Andean valleys in central‐north Peru and separated by ∼1350 km, and extensive high Andean cordilleras above 4000 m, from the nearest populations in Bolivia, represents a genetically highly distinct and morphologically cryptic lineage here described as a new species (Arquita grandiflora). A full taxonomic account of the new genus Arquita and its component species is provided, with a distribution map and a key to the species.

A new generic system for the pantropical Caesalpinia group (Leguminosae)

“…The Caesalpinia group was defined by Polhill and Vidal (1981) to include the genera with species that have a large variety of glandular trichomes, prickles and spines as a defense mechanism, and possessing zygomorphic flowers with a somewhat modified lower sepal and stamens crowded around the pistil. It is currently classified into 21 genera (Lewis 2005), but recent studies, and notably Gagnon et al (2013, 2015), have demonstrated the non-monophly of some of these and the need for a new generic classification (Fig. 1).…”

“…(Simpson et al 2006), Mezoneuron Desf. (Clark and Gagnon 2015), and Arquita E. Gagnon, G. P. Lewis & C. E. Hughes (Gagnon et al 2015). The most recent phylogenetic study (Gagnon et al 2013), based on a single plastid marker ( rps16 ) and sampling 120 of ca.…”

A new phylogeny-based tribal classification of subfamily Detarioideae, an early branching clade of florally diverse tropical arborescent legumes

“…46 . For the most problematic samples, including those with large mononucleotide repeats, we used a PCR protocol with Phusion Hot Start II High-Fidelity DNA polymerase (Thermo Scientific, Waltham, Massachusetts, U.S.A.), which is more accurate and yields longer and higher-quality mononucleotide sequence reads 47 .…”

“…Based on the Akaike information criterion, the best models identified were GTR + I + G for ITS/5.8 S, TVM + G for matK/trnK and rpL16 , and TPM1 uf + G for trnG-trnG2G . Bayesian analyses were conducted in MrBayes v.3.2 65 , but because it is not possible to specify the exact models for the three plastid regions in MrBayes, we used the reversible-jump MCMC option, which allows sampling of different schemes of nucleotide substitution as part of the MCMC run (nst = mixed) 46 . The Bayesian estimation consisted of two independent runs during 50 × 10 6 generations, sampling trees and parameters every 1000th generation.…”

Contribución a La Flora Vascular Y Vegetación De Los Valles Secos Interandinos De Los Ríos Torobamba (Ayacucho) Y Pampas (Apurímac), Sur Del Perú

“…Adicionalmente, hay áreas importantes al sur de Tarapoto (departamento de San Martín) y en los bosques secos inter-andinos (BSI) ubicados en los valles de los ríos Marañón, Mantaro y Apurímac (Linares-Palomino, 2004, 2006. En los últimos diez años se ha generado valiosa información sobre los BSI (Särkinen et al, 2011;Särkinen et al, 2012;Gagnon et al, 2015;Marcelo-Peña et al, 2015); no obstante, aún se conoce poco sobre la biología de estos bosques secos, tanto en términos descriptivos (florísticos) como funcionales (ecológicos).…”