Conservation genetics of an endangered cycad, Dioon sonorense (Zamiaceae): implications from variation of chloroplast DNA

Abstract

Abstract:The endemic species Dioon sonorense comprises the northernmost group of populations of Dioon, in Sonora, Mexico. Although it is endangered, only the southern populations are protected within a preservation area, while the remaining populations have not been taken into account in management plans or genealogical studies. Describing the intraspecifi c genealogy and the geographical structure of the genetic variation of D. sonorense may help in the identifi cation of units for further conservation. Therefore, the main objective of this study was to describe the intraspecifi c genealogy of populations throughout the range of distribution of the endangered species D. sonorense, using haplotypes of the trnL-F spacer of the cpDNA. In addition, the levels of diversity of the employed molecular marker were estimated. Low levels of variability were recorded and at least two evolutionary units, corresponding to each haplotype, were identifi ed as components of the species. The inclusion of northern populations into conservation programs is recommended. In order to integrate these fi ndings to the genealogy of genus Dioon, trnL-F sequences of all the remaining species were merged and analyzed. An ancestral haplotype with wide distribution was detected in several species and one haplotype in D. sonorense was found shared with its sister species, D. tomasellii. This work represents a fi rst attempt to reconcile a genealogical approach in the identifi cation of important centers of genetic diversity of Mexican cycads. Key words: chloroplast DNA, conservation genetics, Dioon sonorense, endangered species.Resumen: La especie endémica Dioon sonorense representa el grupo de poblaciones más norteño para el género Dioon, en Sonora, México. A pesar de su estatus en peligro de extinción, sólo las poblaciones del sur están protegidas dentro de un área de conservación, mientras que las poblaciones restantes no han sido consideradas en los planes de manejo o en estudios genealógicos. La descripción de la genealogía intraespecífi ca y la estructura geográfi ca de la variación genética de D. sonorense puede ayudar en la identifi cación de unidades evolutivas para su posterior conservación. Por lo tanto, el objetivo principal de este estudio fue describir la genealogía intraespecífi ca de las poblaciones de D. sonorense a lo largo de su rango de distribución, usando los haplotipos del espacio trnL-F del ADNcp. Además, se estimaron los niveles de diversidad genética usando este marcador molecular. Se obtuvieron niveles bajos de variabilidad y se identifi caron al menos dos unidades evolutivas, correspondientes a cada haplotipo que componen a la especie. Se recomienda la inclusión de las poblaciones del norte en los programas de conservación. Con el fi n de integrar estos hallazgos en el contexto de la genealogía del género Dioon, las secuencias del espacio trnL-F de todas las especies restantes fueron combinadas y analizadas. Se detectó un haplotipo ancestral con una amplia distribución en varias especies y un haplotipo en D. sonore...

Impact of Late Pleistocene-Holocene climatic fluctuations on the phylogeographic structure and historical demographics of Zamia prasina (Cycadales: Zamiaceae)

“…The number of samples analysed also can influences the amount of genetic diversity detected. In cycads, a range of sample sizes have been used for phylogeographic studies, for example, one individual was used per population for Dioon sonorense (Zamiaceae), and moderate values of nucleotide diversity (h = 0.629) were obtained using the chloroplast region trnL-trnF (Gutiérrez-Ortega et al 2014). For Zamia paucijuga (Zamiaceae) with 8-10 individuals per population, high haplotid diversity was found using ITS2 (h = 0.843) and moderate diversity for the chloroplast region psbK-psbI (h = 0.669) (Nolasco-Soto et al 2015).…”

“…for Z. paucijuga, with h = 0.669 and π = 0.0013 for the chloroplast region psbK-psbI and h = 0.843 and π = 0.0063 for ITS2. For Dioon sonorense,Gutiérrez-Ortega et al (2014) reported h = 0.629 and π = 0.0004 for the chloroplast region trnL-trnF. For the cycads in Mexico, there are reports of high genetic diversity in some species, with few populations and restricted habitats, as in the case of Zamia loddigesii Miq (González-Astorga et al 2006),.…”

Morphometric and geographical variation in theCeratozamia mexicanaBrongn. (Zamiaceae) complex: evolutionary and taxonomic implications

“…Either through the lens of 'classical' population genetics (Gonz alez-Astorga et al, 2003b, 2005, 2006 or through phylogeography (Huang et al, 2001;Chiang et al, 2009;Kyoda & Setoguchi, 2010;Zhan et al, 2011;Guti errez-Ortega, Kajita & Molinar-Freaner, 2014;Nolasco-Soto et al, 2015), the results of further work in this direction will allow the construction of ancestor-descendant hypotheses involving known populations, as well as the assessment of demographic history and genetic differentiation between these populations. In accordance with our population-genetic research programme, evolutionary inferences derived from these phylogeographical interventions will constitute the starting point in species recognition and circumscription.…”

<div class="page" title="Page 1"><div class="layoutArea"><div class="column">Species definition of Dioon sonorense (Zamiaceae, Cycadales), and description of D. vovidesii, a new cycad species from northwestern Mexico </div></div></div>

“…However, although the proposal of Chemnick et al (1997) to segregate D. sonorense from D. tomasellii was persuasive, the definition of D. sonorense only relies on the traits observed in the holotype of D. tomasellii var. sonorense of De Luca et al (1984), in spite that multiple authors (Sabato & De Luca 1985, Whitelock 2002, Gutiérrez-Ortega et al 2014, 2018c have reported important morphological variation among populations. During our field surveys in Sonora, Mexico, we confirmed such variation, especially when comparing the extremes of the distributional ranges of D. sonorense.…”

“…We have also evaluated the patterns of genetic variation among the Dioon populations in northwestern Mexico. The variation of chloroplast DNA (cpDNA) revealed two haplotypes (Gutiérrez-Ortega et al 2014, 2018a. One haplotype represents the populations from the Municipality of Álamos, Sonora, and the area of Río Fuerte in Northern Sinaloa; another haplotype is present in the populations from Municipality of Rosario to Sierra de Mazatán in central Sonora (Gutiérrez-Ortega et al 2014, 2018c.…”