Genetic structure of Anogeissus dhofarica (Combretaceae) populations endemic to the monsoonal fog oases of the southern Arabian Peninsula

Abstract

Anogeissus dhofarica (Combretaceae) is an endemic tree of the monsoon affected coastal mountains of the southern Arabian Peninsula, being the character species of the Hybantho durae-Anogeissetum dhofaricae association, a drought deciduous, monsoon forest community found only in the Dhofar region of southern Oman and the eastern Al-Mahra region of south-east Yemen. Due to the steep precipitation gradient from the centre to the edges in this monsoon affected area, A. dhofarica is found in two different habitat types: in continuous woodland belts of the Hawf and Dhofar mountains, and in isolated, scattered woodland patches, as found especially in the Fartak Mts (south-east Yemen). Fifteen populations (212 individuals) from across the whole distribution area of the species were analysed using amplified fragment length polymorphism fingerprinting to: (1) evaluate the consequences of population fragmentation on the genetic diversity harboured in isolated patches versus cohering stands of the species and (2) to reconstruct the phylogeographical pattern of A. dhofarica as a consequence of oscillations in the monsoon activity during the Pleistocene and Holocene. The analysis of among-population genetic differentiation and within-population genetic diversity in A. dhofarica populations resulted in a lack of genetic pauperization and genetic differentiation of populations of the distinctly isolated patches of the Fartak Mts compared to the more luxurious forests of the Hawf and Dhofar regions. This is considered to be due to the high buffer capacity against the loss of genetic diversity caused by the long-lived life-form of the species combined with the capability to propagate clonally and the relatively recent fragmentation of Anogeissus forests into the described patches rather than due to high values of gene flow among remnant populations caused by bee pollination and anemochorical and hydrochorical diaspore dispersal. The phylogeographical pattern of the species argues for a quite recent fragmentation of a once continuous forest belt of A. dhofarica that is rather connected with climate changes in the Holocene than triggered by aridity-humidity oscillations reported for the Pleistocene.

Combining multiple analytical approaches for the identification of population structure and genetic delineation of two subspecies of the endemic Arabian burnet moth Reissita simonyi (Zygaenidae; Lepidoptera)

“…Meister et al (2006 dated the main split between the western distribution areas of J. areysiana (corresponding to the distribution area of R. s. yemenicola) and the south-eastern distribution areas in Yemen and Oman (corresponding to the patchy distribution area of R. s. simonyi) to 0.8-1.8 Mya. Although a dating has been not possible in the present work, the common pattern is striking and strongly indicates ancient habitat fragmentation due to cycles of aridification during the Pleistocene (Oberprieler et al 2009). …”

“…Importantly, the stronger population structure found in R. s. simonyi may be highly linked to the monsoonal fog oases of the southern Arabian Peninsula (Oberprieler et al 2009), because the larval host plant of R. simonyi is only found in these patches similar to other plants species like Justicia areysiana (Meister et al 2005(Meister et al , 2006 and Euclea schimperi (Meister et al 2008). Meister et al (2006 dated the main split between the western distribution areas of J. areysiana (corresponding to the distribution area of R. s. yemenicola) and the south-eastern distribution areas in Yemen and Oman (corresponding to the patchy distribution area of R. s. simonyi) to 0.8-1.8 Mya.…”

Genetic structuring of remnant forest patches in an endangered medicinal tree in North-western Ethiopia

“…However, empirical research has documented contradictory genetic effects of habitat loss and fragmentation especially on long-lived tree species [ 18 ]. That is to say, some studies have shown adverse effects of habitat loss and fragmentation on the genetic diversity and structure of various tree species [ 19 - 22 ] whereas others did not find genetic effects of forest fragmentation [ 23 - 25 ]. The absence of genetic effects of fragmentation among long-lived tree species is most likely due to the recent history of human disturbance and fragmentation events whose genetic effects will only be reflected after multiple generations which might not have been accounted for by some researchers [ 26 ].…”

The Conservation Status and Population Mapping of the Endangered Dracaena serrulata in the Dhofar Mountains, Oman

“…The precipitation and cooling effect provided by the summer monsoon isa driving force for the unique and diverse vegetation of the Dhofar Mountains [32,[43][44][45]. The areas most affected by the summer monsoon are the southwest facing slopes of the Dhofar Mountains, particularly the escarpment cliffs on Jabal al Qara and al Qamar.…”