Taxonomic reevaluation of the Polylepis sericea complex (Rosaceae), with the description of a new species

The taxonomically difficult genus Polylepis (Rosaceae) contains several problematic species complexes, including one around P. sericea. We here reevaluate species boundaries in this complex based on morphological characters and climatic niches. We recognize five species within the P. sericea complex, based primarily on leaf characters: P. albicans (northwestern Peru), P. argentea (central Peru) described here, P. canoi (southeastern Peru to central Bolivia), P. ochreata (Ecuador to southernmost Colombia), and P. sericea (Venezuela to central Colombia). We provide full synonymy, diagnostic notes, lists of selected specimens examined, and a key to the species of the complex

Taxonomic Reevaluation of the Polylepis sericea Complex (Rosaceae), with the Description of a New Species

The taxonomically difficult genus Polylepis (Rosaceae) contains several problematic species complexes, including one around P. sericea. We here reevaluate species boundaries in this complex based on morphological characters and climatic niches. We recognize five species within the P. sericea complex, based primarily on leaf characters: P. albicans (northwestern Peru), P. argentea (central Peru) described here, P. canoi (southeastern Peru to central Bolivia), P. ochreata (Ecuador to southernmost Colombia), and P. sericea (Venezuela to central Colombia). We provide full synonymy, diagnostic notes, lists of selected specimens examined, and a key to the species of the complex

Estructura forestal de tres especies endémicas del género Polylepis (Rosaceae) en la Región Central del Perú

Polylepis (Rosaceae) is the dominant tree genus in High-Andean forest ecosystems. These ecosystems are severely threatened, but litle is known about their structure and functioning. We provide the first reports of the dasometric structure and spatial distribution of eight forests of Polylepis canoi, P. flavipila and P. rodolfo-vasquezii in the Central Peruvian Andes as fundamental information for management and conservation policies. We sampled all individuals ≥1 cm of diameter at ground level (DGL) in 20 plots of 10x10 m in each forest, and measured total height (TH) and DGL. Also, we mapped the spatial distribution of the individuals in two plots of 30x30 m (X and Y axes). We found differences in the dasometric structure between forests of the same species, which, in some cases, were associated with climate, soil or elevation variables. However, no well-defined pattern was found. The allometric relationships of the linear and non-linear models did not differ widely with respect to the R2 nor to the Akaike (AIC) scores, indicating that the forests did not show a saturation of tree height with increasing diameter. In the P. canoi forests, individuals with diameters ≥10 cm were the most abundant. In contrast, the forests of P. rodolfo-vasquezii showed a predominance of individuals with diameters ≤10 cm, whereas P. flavipila presented an altered structure with no relationship between DGL and TH in one of the evaluated forests. The analysis of spatial distribution according to the Ripley’s K function on a small scale revealed that P. flavipila and P. canoi presented random patterns, whereas P. rodolfo-vasqueziishowed an aggregate pattern. Finally, our results showed that even forests of the same species have different dasometric structures, whereas spatial patterns differ only between species. So, caution must be taken when extrapolating information between species or forests during ecological studies and conservation actions

Using dendrochronology to trace the impact of the hemiparasite Tristerix chodatianus on Andean Polylepis trees

The high Andean forests of the genus Polylepis (Rosaceae) are threatened by extinction due to anthropogenic effects such as timber extraction, burning, and overgrazing. Some species are also affected by Tristerix chodatianus (Loranthaceae), a hemiparasitic plant which induces progressive host damage. To understand this hemiparasitic process, we evaluated the impact of T. chodatianus on growth and the wood anatomy of Polylepis flavipila using growth rings and digital image processing. We found that P. flavipila has a xeromorphic wood anatomy and that the ecological indices of mesomorphism and vulnerability decrease at higher elevations to avoid embolisms and vessel cavitation. Tristerix chodatianus causes anatomical changes in the host wood, mainly in the last 13 years measured. Alterations include a reduction in the vessel density, and an increase in the vessel diameter and Vulnerability Index, all of which are more evident in downstream sections of parasitized branches. These changes in the xylem tissues increase the vulnerability of the parasitized branches to embolisms and cavitation, thus leading to progressive death of the tree crown. Our study confirms that the analysis of the wood anatomy of parasitized branches can be used to determine the years of colonization of a tree branch by a hemiparasite and that it can be a useful tool to monitor the phytosanitary state of parasitized Polylepis trees

Age structure and climate sensitivity of a high Andean relict forest of Polylepis rodolfo-vasquezii in central Peru

For a better understanding of forest ecology, tree-ring studies can provide information on climate sensitivity, tree growth patterns and population age structure that can inform about stand dynamics such as recruitment of new individuals, and other interspecific interactions related to competition and facilitation. Little is known about the ecology of the recently identified high Andean tree species Polylepis rodolfo-vasquezii. Here, we analyzed the relationship between tree size and age of two P. rodolfo-vasquezii forest stands located in the central Peruvian Andes at 11°S in latitude, and compared their growth patterns and climate sensitivity. We measured the height and diameter of each individual tree and collected tree core samples of living trees and cross sections of dead standing trees to generate two centennial tree-ring chronology at Toldopampa (1825–2015 CE) and at Pomamanta (1824–2014 CE) sites. The dendrochronological dates were evaluated by 14C analysis using the bomb-pulse methods analyzing a total of 9 calendar years that confirm the annual periodicity of this tree species. At the Toldopampa stand most trees ranged from 70 to 80 years old, with a 190-year old individual, being an older and better preserve forest than Pomamanta, with younger trees, probably because more human disturbances due to closer village proximity. No significant relationships were found between tree age and size in the oldest stand alerting that tree diameter should not be used as a metric for estimating tree ages as a general rule. The distinct growth patterns and the size-age relationship observed at the two forests may reflect distinct histories regarding human activities such as fire and logging. Nevertheless, both the Toldopampa and the Pomamanta tree-ring width chronologies exhibited common growth patterns and shared a similar positive response to temperature of the current growing season. Overall, our study confirmed the annual radial growth periodicity in P. rodofolfo-vasquezii trees using an independent method such as 14C analyses and a strong climate sensitivity of this tree species. These findings encourage the development of an extensive P. rodolfo-vasquezii tree-ring network for ecological and paleoclimate studies in the tropical Andes in South America.Fil: Ticse Otarola, Ginette Vilma Alicia. Universidad Continental; PerúFil: Vidal, Osir D.. Universidad Continental; PerúFil: Andreu Hayles, Laia. Consejo Superior de Investigaciones Científicas. Centre de Recerca Ecológica I Aplicacions Forestals; España. Institució Catalana de Recerca i Estudis Avancats; España. Columbia University; Estados UnidosFil: Quispe Melgar, Harold R.. Asociación ANDINUS; Perú. Universidad Continental; PerúFil: Amoroso, Mariano Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural. - Universidad Nacional de Rio Negro. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural; ArgentinaFil: Santos, Guaciara M.. University of California at Irvine; Estados UnidosFil: Requena Rojas, Edilson Jimmy. Universidad Continental; Per