Magnolia mercedesiarum (subsect. Talauma, Magnoliaceae): a new Andean species from northern Ecuador, with insights into its potential distribution

Abstract

Magnolia mercedesiarum, a new species from the eastern slopes of the Andes in northern Ecuador, is described and illustrated, and a key to Ecuadorian Magnolia (subsect. Talauma) is provided. This species differs from M. vargasiana in having broadly elliptic leaves that have an obtuse base vs. suborbicular and subcordate to cordate, glabrous stipular scars, more numerous lateral veins per side and fewer stamens. It also differs from M. llanganatensis in having leaf blades broadly elliptic vs. elliptic, longer petioles, less numerous lateral leaf veins per side, larger fruits and more numerous petals and carpels. Using MaxEnt species distribution models and IUCN threat criteria, M. mercedesiarum has a potential distribution area of less than 3307 km² and is assessed as Endangered (EN): B1 ab (i, ii, iii). The relevance of systematic vegetation sampling in the discovery of rare species is highlighted. ResumenMagnolia mercedesiarum es descrita e ilustrada como especie nueva nueva de la vertiente oriental de los Andes en el norte de Ecuador. Se incluye una clave para las especies ecuatorianas de Magnolia. Esta especie se diferencia de M. vargasiana por tener hojas elípticas a ampliamente elípticas de base obtusa vs. suborbiculares (rara vez anchamente elípticas) de base subcordada a cordada, cicatriz de estipular glabra, mayor número de nervios laterales por lado de la hoja y menor número de estambres. Esta especie se diferencia de Magnolia llanganatensis por tener láminas foliares ampliamente elípticas vs. elíp-ticas a angóstamente elípticas, pecíolos más largos, menos venas foliares por lado; frutos más grandes y pétalos y carpelos más numerosos. Mediante el uso de los modelos de distribución de especies MaxEnt y los criterios de amenaza de la IUCN, M. mercedesiarum tuvo una área de distribución potencial menor de 3307 km² y fue diagnosticada como En Peligro (EN): B1 ab (i, ii, iii). Se resalta la relevancia de levantamientos sistemáticos de vegetación en el descubrimiento de especies raras.

Vulnerability to climate change for narrowly ranged species: the case of Ecuadorian endemicMagnolia mercedesiarum

“…Although the environmental niche model produced in this study is partial, it demonstrates high correlation in geographic prediction with distribution estimation from Vázquez-García et al (2018), produced with the same predictors, treated here as true species distribution. Independently from the fidelity of the source species distribution estimation, the research question addressed in this article is how such narrow distribution could change in HadGEM2-ES climate projections for two CO2 emission scenarios.…”

“…The lack of reproduction function may be an indication for populations that they may not belong to stable "core" areas with habitat condition characteristics for the species' fundamental niche, but their belonging to less stable sink areas that depend on individuals' immigration from sources, at the current moment or in the immediate past. All observations of M. mercedesiarum cited in Vázquez-García et al (2018) were made on trees bearing flowers or fruits, although no saplings were noted beneath the observed trees. Guisan and Thuiller (2005) affirm that populations without evidence of sexual reproduction are preferable to exclude from the training data in SDM because they can be assumed to lack the positive growth rate for population size and may be located beyond the specific climatic thresholds.…”

“…The current distribution of Magnolia mercedesiarum of 2701 km 2 taken from Vázquez-García et al (2018), as shown in Fig. 2, was found to lie in the elevation range of 1075-2576 m above the sea level; 90% of presence points are restricted to 1237-2264 m, with a median at 1736 m according to the GMTED2010 dataset.…”

“…This process occurs because part of the background points may actually correspond to presences, and the fact MaxEnt appends presence points to the background dataset during AUC calculation Elith et al, 2011). In this study, we treat the probable current distribution of M. mercedesiarum taken from Vázquez-García et al (2018) as the known realized distribution of species, therefore, in model evaluation, we deal with true presences and absences suitable for real AUC calculation. In this way, we determine the real AUC for model prediction in current conditions without violation of the underlying theory that requires use of true absences in model evaluation (Lobo et al, 2007;Jiménez-Valverde, 2012).…”

“…1), naturally occurring in the moist tropical mountainous forests in the eastern slopes of the Andes in Ecuador. As stated in Vázquez-García et al (2018), this species is currently known from only four localities in the Napo and Sucumbíos Ecuadorian provinces and has an extremely narrow distribution range; thus, it fulfills the International Union for Conservation of Nature (IUCN 2012) Red List criteria B1 ab (i, ii, iii) for an endangered (EN) species.…”