Genetic imprints of Brosimum alicastrum Sw. in Mexico

Abstract

The mechanisms generating the geographical distributions of genetic diversity are a central theme in evolutionary biology. The amount of genetic diversity and its distribution are controlled by several factors, including dispersal abilities, physical barriers, and environmental and climatic changes. We investigated the patterns of genetic diversity and differentiation among populations of the widespread species Brosimum alicastrum in Mexico. Methods: Using nuclear DNA microsatellite data, we tested whether the genetic structure of B. alicastrum was associated with the roles of the Trans-Mexican Volcanic Belt and the Isthmus of Tehuantepec as geographical barriers to gene flow and to infer the role of past events in the genetic diversity patterns. We further used a maximumlikelihood population-effects mixed model (MLPE) to identify the main factor affecting population differentiation in B. alicastrum. Results: Our results suggested that Mexican B. alicastrum is well differentiated into three main lineages. Patterns of the genetic structure at a finer scale did not fully correspond to the current geographical barriers to gene flow. According to the MLPE mixed model, isolation by distance is the best model for explaining the genetic differentiation of B. alicastrum in Mexico. Conclusions: We propose that the differentiation patterns might reflect (1) an ancient differentiation that occurred in Central and South America, (2) the effects of past climatic changes, and (3) the functions of some physical barriers to gene flow. This study provides insights into the possible mechanisms underlying the geographic genetic variation of B. alicastrum along a moisture gradient in tropical lowland forests.

Genomic diversity and structure of a Neotropical microendemic fig tree

“…Patterns of gene flow revealed by FEEMS could be attributable to geography, particularly the uplands to the west of TMVB and Sierra Madre del Sur, which had been previously identified by analyzing gene flow patterns for several species found on both sides of the TMVB (Anguiano‐Constante et al., 2021 ; Gándara & Sosa, 2014 ; López‐Barrera et al., 2021 ; Ruiz‐Sanchez & Ornelas, 2014 ). However, there is low differentiation between individuals north and south of the TMVB in F .…”

“…In this area, it has been suggested that recent mountainous complexes, such as the Trans‐Mexican Volcanic Belt (TMVB), are main drivers of diversification in Mexico and have affected taxa in different ways (Mastretta‐Yanes et al., 2015 ). For example, in the lowlands, the TMBV has functioned as a barrier by introducing a genetic discontinuity in several species with different dispersal capabilities (Arbeláez‐Cortés et al., 2014 ; López‐Barrera et al., 2021 ; Schramm et al., 2021 ; Zarza et al., 2008 ). However, the pattern of genetic diversity and structure in the Ficus species of this region is unknown.…”

Gone with the wind: Negative genetic and progeny fitness consequences of habitat fragmentation in the wind pollinated dioecious treeBrosimum alicastrum

“…Sex ratios were unbiased in all but one site (Zapata), in which the sex ratio was female biased (Table 1). In fragmented areas, B. alicastrum individuals are large remnant trees in small aggregations along rivers within agricultural landscapes, used by local people either as shade trees or for harvesting fruits (López‐Barrera et al, 2021). Thus, a female‐biased sex ratio in Zapata was probably associated with more intensive land use and selection of female trees for fruit harvest.…”

“…In fragmented areas, B. alicastrum individuals are large remnant trees in small aggregations along rivers within agricultural T A B L E 2 Genetic diversity estimates for each habitat condition and developmental stage of Brosimum alicastrum in two habitat conditions in the region of the Chamela-Cuixmala Biosphere Reserve, Jalisco, Mexico. landscapes, used by local people either as shade trees or for harvesting fruits (López-Barrera et al, 2021). Thus, a femalebiased sex ratio in Zapata was probably associated with more intensive land use and selection of female trees for fruit harvest.…”

“…We extracted DNA from leaves using the commercial "DNEasyTM Plant Mini Kit" (QIAGEN, Hilden, Germany), following the manufacturer's specifications. Eight microsatellite loci previously developed for B. alicastrum (López-Barrera et al, 2021) were amplified via multiplex polymerase chain reaction (PCR) using the QIAGEN Multiplex Kit (QIAGEN, Hilden, Germany) in a 8.29 µL final volume containing: 0.3 μL of DNA template, 0.83 μL of primers (0.2 μM), 3 μL of H 2 O and 4.16 μL of Multiplex PCR Master Mix (QIAGEN, Hilden, Germany). The PCR amplification was performed in a GeneAmp PCR System 9700 thermal cycler (Applied Biosystem, Carlsbad, California, USA) using the following conditions: an initial activation step of 95°C for 15 min, followed by 35 cycles of denaturation at 95°C for 30 s; annealing for 30 s at 60°C; elongation at 72°C for 60 s; and a final extension at 72°C for 10 min.…”