Niche Divergence versus Neutral Processes: Combined Environmental and Genetic Analyses Identify Contrasting Patterns of Differentiation in Recently Diverged Pine Species

Abstract

Background and AimsSolving relationships of recently diverged taxa, poses a challenge due to shared polymorphism and weak reproductive barriers. Multiple lines of evidence are needed to identify independently evolving lineages. This is especially true of long-lived species with large effective population sizes, and slow rates of lineage sorting. North American pines are an interesting group to test this multiple approach. Our aim is to combine cytoplasmic genetic markers with environmental information to clarify species boundaries and relationships of the species complex of Pinus flexilis, Pinus ayacahuite, and Pinus strobiformis.MethodsMitochondrial and chloroplast sequences were combined with previously obtained microsatellite data and contrasted with environmental information to reconstruct phylogenetic relationships of the species complex. Ecological niche models were compared to test if ecological divergence is significant among species.Key Results and ConclusionSeparately, both genetic and ecological evidence support a clear differentiation of all three species but with different topology, but also reveal an ancestral contact zone between P. strobiformis and P. ayacahuite. The marked ecological differentiation of P. flexilis suggests that ecological speciation has occurred in this lineage, but this is not reflected in neutral markers. The inclusion of environmental traits in phylogenetic reconstruction improved the resolution of internal branches. We suggest that combining environmental and genetic information would be useful for species delimitation and phylogenetic studies in other recently diverged species complexes.

On the origins of Balkan endemics: the complex evolutionary history of theCyanus napulifergroup (Asteraceae)

“…Recent investigations into the tribe Carduae (Barres et al, 2013) and the genus Centaurea (Hilpold et al, 2014) estimated by molecular dating that the crown diversification between Cyanus annuals and perennials as well as between the two chromosome lineages (x ¼ 10 and x ¼ 11) of Cyanus perennials dates back to the late Tertiary (Late Miocene/Pliocene; $3Á8-8Á8 million years ago). The extensive sharing of plastid haplotypes among accessions of both chromosome lineages detected in our study thus suggests that there was not enough time between each speciation event for informative mutations to emerge and for lineage sorting to take place (Jakob and Blattner, 2006;Maddison and Knowles, 2006;Moreno-Letelier et al, 2013). The presence of insufficient or contradictory phylogenetic signals may in this case also be attributed to the maintenance of ancestral variation formed by rapid radiation during the first phases of group diversification or, alternatively, to ancient introgression between distinct populations or genetic lineages (e.g.…”

Modelado de nicho ecológico de las especies del género Abies (Pinaceae) en México: Algunas implicaciones taxonómicas y para la conservación

“…en relación con su importancia como refugio de la mariposa monarca y las afectaciones ante distintos escenarios de cambio climático. Los otros estudios existentes se enfocan en utilizar el modelado de nicho ecológico como herramienta auxiliar para explicar algunos patrones filogeográficos (Gugger et al, 2011;Moreno-Letelier et al, 2013), pero ninguno de los estudios mencionados ha sido enfocado explícitamente como una método auxiliar en la delimitación de especies.…”

“…Los ciclos de aislamiento y contacto arriba mencionados probablemente estuvieron mediados por el "seguimiento ecológico" que las poblaciones de abetos hicieron de las condiciones templadas características de sus nichos. Este seguimiento ecológico parece haber influenciado los patrones genéticos y de distribución de poblaciones de muchas otras coníferas (Gugger et al, 2011;Moreno-Letelier et al, 2013) y ha sido sustentado con datos palinológicos que indican que los bosques templados de Mesoamérica se extendieron por debajo de los 1,000 m s.n.m. durante el último máximo glacial hace unos 21 ± 2 ka (Bush et al, 2009).…”

“…Posteriormente, Sáenz-Romero et al (2012) modelaron el nicho ecológico de Abies religiosa en relación con su importancia como refugio de la mariposa monarca y las afectaciones ante distintos escenarios de cambio climático. Los otros estudios existentes se enfocan en utilizar el modelado de nicho ecológico como herramienta auxiliar para explicar algunos patrones filogeográficos (Gugger et al, 2011;Moreno-Letelier et al, 2013). Es así que la importancia de este trabajo radica en que los datos aquí generados son los primeros en comparar ecológi-camente a casi todas las especies de abetos en México y nos ayudarán a poner a prueba distintas hipótesis filogeográficas y al mismo tiempo obtener datos de partida para estudios de conservación y cambio climático (ver más adelante).…”

Mosaic genetic differentiation along environmental and geographic gradients indicate divergent selection in a white pine species complex

“…We focus on a small species complex of North American white pines that diverged around 2.8 Mya (Moreno-Letelier et al 2013): Pinus flexilis (James), Pinus strobiformis (Engelmann), and Pinus ayacahuite (Ehrenberg ex Schlechtendahl). These species are distributed along a latitudinal and environmental gradient that goes from the Canadian Rocky Mountains in the North, to the Highlands of Guatemala and Honduras to the South ( Fig.…”