Genetic diversity of the great bustard in Iberia and Morocco: risks from current population fragmentation

Abstract

We studied the genetic diversity of great bustards (Otis tarda) in Iberia and Morocco, the main stronghold of this globally endangered species. Samples were collected from 327 individuals covering most of the distribution range within the study area. Sequence variation in a 657 bp fragment of the mtDNA control region revealed 20 variable sites defining 22 haplotypes, two of them exclusive to Morocco. Genetic diversity showed marked regional differences (p = 0-0.53, h = 0-0.89). Multidimensional scaling analysis based on F ST values showed a clear division between Morocco and the Iberian Peninsula, with no evidence of current gene flow between them. Our results suggest that Morocco, where few matrilines have persisted to present, was colonized from Iberia thousands of years ago. Last century reports suggest dispersal through Gibraltar, when the species was more abundant at both sides of the Strait but later population declines and the Strait's barrier effect have favoured current genetic isolation. Within Iberia, only the most peripheral populations (Navarra, Aragón and Andalusia) differed significantly from the main ones in central Spain. The first two showed extremely low genetic diversity and are probably threatened by inbreeding depression. Diversity was higher in Andalusia, where three exclusive haplotypes were found, suggesting some degree of isolation from other populations. Andalusia and Morocco could be regarded as separate management units which hold a significant proportion of the current genetic diversity and thus deserve urgent conservation measures.

Genetic structure in Iberian and Moroccan populations of the globally threatened great bustardOtis tarda: a microsatellite perspective

“…Although results from STRUCTURE and BAPS should be interpreted with caution in cases of low differentiation, our data reveal two main genetic clusters within Iberia, which separate the northeastern part of Spain in the Ebro River valley, from the rest of the populations. Previous mitochondrial studies had detected very low levels of genetic diversity in the northeast and had identified this region as an area of special concern (Alonso et al , Pitra et al ). Genetic diversity in nuclear markers is not lower than that found in other parts of the range, suggesting that male dispersal capacity may compensate for female philopatry, maintaining allele diversity and potentially buffering the population against sudden environmental changes (Frankel and Soulé ).…”

Impact of habitat fragmentation on the genetics of populations in dendritic landscapes

“…Population genetic structure is strongly influenced by habitat fragmentation in a variety of animals, including birds (e.g. Otis tarda L.; Alonso et al, 2009) and fishes (e.g. Cottus gobio; Hänfling & Weetman, 2006).…”

Linking habitat quality with genetic diversity: a lesson from great bustards in Spain

“…Spanish great bustards form a metapopulation of several subpopulations with various degrees of interconnection among them (Martín et al 2002;Alonso et al 2009). The patch sizes occupied by these subpopulations are significantly correlated with the respective bird numbers.…”

“…Parallel to an ongoing population decline during the 20th century throughout Europe, the Spanish population of the great bustard has fragmented in several breeding areas distributed across the regions of Madrid, Castilla-La Mancha, Extremadura, Castilla y León, Navarra, Aragón and Andalusia (Alonso et al 2003). Populations at the periphery (the last three mentioned previously) were the most genetically differentiated from the main ones in central Spain (Alonso et al 2009). Accordingly, peripheral populations are also found to be more susceptible to decline and extinction than populations at the core of their range Alonso et al 2005).…”

“…The Iberian peninsula is home to~27,500-30,000 great bustards, approximately 60% of the world population of this species (Palacín and Alonso 2008). For great bustards in Spain, metapopulation structure has recently been shown based on ecological surveys (Alonso and Alonso 1996;Alonso et al 2003Alonso et al , 2004 and genetic analyses (Martín et al 2002;Alonso et al 2009). The birds occupy patches of open, steppe-like landscapes with cerealfallow rotations, a habitat that is particularly under threat because of agriculture intensification and land abandonment linked to the European agricultural policy.…”