Ecological implications of Cousinia Cass. (Asteraceae) persistence through the last two glacial-interglacial cycles in the continental Middle East for the Irano-Turanian flora

Review of Palaeobotany and Palynology (Impact Factor: 1.94). 02/2012; 172. DOI: 10.1016/j.revpalbo.2012.01.005


This study explores the response of the Irano-Turanian flora to Quaternary glacial–interglacial cycles in SW Asia. We use new fossil pollen data to assess variation in abundance of Cousinia Cass. (Compositae), a large genus typical for the Irano-Turanian flora, during these cycles. The results are compared with modern topography, tectonic and palaeoclimatic history, and recent phylogenetic data to explain the extremely high speciation rate and level of endemism as well as the modern geographical distribution of the genus. Cousinia is consistently well-represented in glacial-age and late-glacial pollen assemblages of NW Iran and E Anatolia. In the ~ 200,000-year pollen sequence from Lake Urmia, NW Iran, Cousinia pollen shows significant values and is nearly continuously represented during both the last glacial (~ 70 ka to Holocene) and penultimate glacial periods (~ 190 to 130 ka). In contrast, its pollen is less frequent and occurs only sporadically during the last interglacial period and the Holocene. This pattern suggests that Cousinia could not only withstand Quaternary glaciations, but was a significant part of the glacial-age landscapes of the Irano-Turanian territory. We argue that the extremely high rate of speciation and endemism of Cousinia is due to (i) the continuous presence of a complex topography in the Middle East and Central Asia since Tertiary times, which created a wide range of environmental niches and facilitated the formation and persistence of isolated populations over long periods, (ii) relatively stable climate during the late Miocene–Pliocene compared to the Quaternary period that caused small species range shifts and gene flow, and (iii) a dampened impact of multiple glacial–interglacial cycles on the mountain regions of SW Asia compared to the higher latitude European mountain ranges. This left an extensive, non-glaciated altitudinal zone for the survival of Irano-Turanian species, thereby reducing extinction during glacial periods. During interglacial periods, many Cousinia species may have been geographically isolated in high mountain “interglacial refugia” of the Irano-Turanian region. Overall, the combination of the above factors during the Neogene resulted in geographical isolation and reduced gene flow, thereby fostering allopatric speciation in Cousinia and probably also in many other speciose Irano-Turanian plant taxa.

Download full-text


Available from: Sara López-Vinyallonga
  • Source
    • "2.6 Mya, Late Plio- cene; Popescu, 2006 ) favored continent-wide open steppe vegetation with a high diversity of xerophytic plants (Suc, 1984; Suc et al., 1995; Thompson, 2005; Pérez-Collazos et al., 2009). During these interglacial periods, including the present one, it is assumed that the range of steppe plants contracted to refugia, such as those found at particular altitudes (Djamali et al., 2012; Gentili et al., 2015). Among these xerophyte taxa, thorny cushion-like plants from the Fabaceae family have a strong ecological importance among Mediterranean steppe flora. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Understanding the origin and evolution of Mediterranean vascular flora within the long-term context of climate change requires a continuous study of historical biogeography supported by molecular phylogenetic approaches. Here we provide new insights into the fascinating but often overlooked diversification of Mediterranean xerophytic plants. Growing in some of the most stressing Mediterranean environments, i.e. coastal and mountainous opened habitats, the circum-Mediterranean Astragalus L. sect. Tragacantha DC. (Fabaceae) gathers several thorny cushion-like taxa. These have been the subjects of recent taxonomical studies, but they have not yet been investigated within a comprehensive molecular framework. Bayesian phylogenetics applied to rDNA ITS sequences reveal that the diversification of A. sect. Tragacantha has roots dating back to the Pliocene, and the same data also indicate an eastern-western split giving rise to the five main lineages that exist today. In addition, AFLP fingerprinting supports an old east-west pattern of vicariance that completely rules out the possibility of a recent eastern origin for western taxa. The observed network of genetic relationships implies that contrary to what is widely claimed in the taxonomic literature, it is range fragmentation, as opposed to a coastal-to-mountain ecological shift, that is likely the main driver of diversification.
    Full-text · Article · Jan 2016 · Molecular Phylogenetics and Evolution
  • Source
    • "Although considerable research has been devoted recently to improve the understanding of ecology, biogeography and phylogeography of the flora of Iran (e.g. Klein 2001; Akhani 2011; Djamali et al. 2012a, b; Manafzadeh et al. 2013), substantial gaps in knowledge prevail. For instance, even recently several vascular plant species were described as new to science from Iran (e.g. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Mountain ranges cover around one-half of the territory of Iran. Although it is well-known that these mountains are characterized by high levels of endemism, no assessment of vascular plant endemism of Iranian mountains has been made. Here, we undertake a first analysis of the diversity and biogeography of high-altitude (=taxa, whose elevational distribution ranges are entirely or largely above 2500 m a.s.l.) endemic vascular plant species restricted to Iran. In total, our data set includes 569 endemic vascular plant taxa (incl. 43 subendemic taxa which slightly extend into adjacent countries), which correspond to 62 % of the entire alpine flora. The highest number of alpine endemics occurs in the Zagros, followed by Alborz, and the NW Iranian mountains. Screes, rocks and thorn-cushion grasslands are the most important habitats for the alpine endemics. The altitudinal distribution of Iranian endemic alpine plant taxa peaks at high altitudes at c. 3000 m a.s.l. Below and above this altitude, there is a steep decrease in endemic alpine species numbers. The analysis of description histories in time-to-event analysis framework suggests that the rate by which new Iranian endemic alpine plant species are described does not seem to level off. Therefore, the proportion of species that still remain to be described is difficult to estimate. However, time-to-event analysis shows that at least 7 % of the extant Iranian alpine endemic species are not yet known to science. In addition, on average, the time lag between the year of collection and species description was 18 years. We conclude that there is a need for a continued botanical exploration in particular of under-sampled mountain ranges and for taxonomic revisions of genera rich in endemics which have been insufficiently studied yet.
    Full-text · Article · Dec 2015 · Alpine Botany
    • "It contains 600 to 700 species in Southwest and Central Asia. The distribution area of Cousinia is nearly identical with the Irano– Turanian region (Knapp 1987; Djamali et al. 2012) (Fig. 1). The overall number of Cousinia sections and species is difficult to estimate. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Cousinia Cass. is one of the largest genuses in the Asteraceae. It contains 600 to 700 species in Southwest and Central Asia, in Iran with 270 species is the largest genus after Astragalus, Cousinia probably is unique in the degree of diversification of all its parts and definitely unique in the restricted distribution area of a high number of species. Some of Cousinia species have medicinal value. Perhaps the most important biological challenge today is the conservation of biodiversity. As human population increases, so does the need for natural resources and space for the growing population. In this investigation eighty-seven plant specimens of 8 geographical populations of Cousinia tabrisiana Bunge. were studied from morphological and genetic (ISSR) points of view. Both intra and inter-population morphological and genetic variability was observed in the studied populations. ANOVA and CVA tests revealed significant morphological difference among these populations. Similarly, AMOVA and Hickory tests revealed significant molecular difference among geographical populations. Mantel test produced significant positive correlation between genetic distance and geographical distance of the studied populations. Networking, STRUCTURE analysis and population assignment test revealed some degree of gene flow among these populations. LMFF test identified some of the ISSR loci to be correlated with environmental factors studied and consensus tree of morphological and genetic data identified divergent populations.
    No preview · Article · Mar 2015 · Biologia
Show more