Effect of the landscape on functional and spatial connectivity in Magnolia cubensis (Magnoliaceae) in two mountain massifs of Cuba

Majela Hernández Rodríguez,Emily Veltjen,Isabel Larridon,Alejandro Palmarola Bejerano,Ernesto Testé,Luis Roberto González Torres,Jhonny Quintana Delgado,Marie-Stéphanie Samain,Marlyn Valdés De La Cruz,Pieter Asselman

doi:10.1007/s10592-021-01395-6

Abstract

Landscape features impact gene flow and the spatial patterns of genetic variation between populations of a species. Because many Magnoliaceae species occur in fragmented and highly disturbed landscapes, the family provide an excellent model for landscape genetic studies. This research focuses on the subspecies and subpopulations of Magnolia cubensis and aims to: (1) compare the genetic diversity between the different subspecies and their subpopulations, (2) search for patterns between the spatial and genetic distance, (3) quantify the functional connectivity and (4) assess the structural connectivity of the landscape. This study employs 21 microsatellite markers to quantify the genetic diversity, complemented with seven landscape characteristics of the Guamuhaya and Sierra Maestra massifs in Cuba. Magnolia cubensis subsp. acunae does not have a well-defined spatial genetic pattern: there is no evidence of isolation by distance or spatial autocorrelation and the little genetic differentiation between the two subpopulations does not reflect the characteristics of the landscape that separates them or the cost values to cross it. Magnolia cubensis subsp. cubensis presents evidence of isolation by distance and the autocorrelation analyses indicate that the approximate scale of the genetic neighborhood is between 35 and 40 km. There is a marked genetic structure with probability values that indicate the existence of three genetic groups. Large genetic differentiation was only found between Gran Piedra and the other subpopulations, which reflects low gene flow. Our results support the recognition of these subspecies at the species level. We define one evolutionary significant unit in Magnolia cubensis subsp. acunae and two evolutionary significant units in Magnolia cubensis subsp. cubensis. These results must be combined with ecological, social and distribution data, in order to obtain a more accurate and realistic perspective of the conservation management strategies for these taxa.

Highlights

Landscape features impact gene flow and the spatial patterns of genetic variation between populations of the same species (Anderson 2010)
The population structure does not correspond to the demographic groups or the topology of the localities, and the diversity values are not related to the degree of fragmentation of the habitat, but rather to the number of individuals
The little genetic differentiation between the two localities does not reflect the characteristics of the landscape that separates them or the cost values to cross it

Summary

Introduction

Landscape features impact gene flow and the spatial patterns of genetic variation between populations of the same species (Anderson 2010). With the emergence of landscape genetics as a discipline (Manel et al 2003), the ability of genetic markers to quantify genetic diversity is being combined with spatial data (Scribner et al 2005; Apodaca et al 2012; Frantz et al 2012). Most studies did not consider the landscape, and only a few studies have compared Magnolia genetic diversity with the underlying spatial data (Kikuchi and Isagi 2002; Isagi et al 2007; Hernández et al 2020a) These studies are approximations to the description of genetic patterns in geographical space, they lack an integrative analysis between genetic variation patterns and the landscape or environment characteristics

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Conclusion