The life history of Salicaceae living in the active zone of floodplains

Abstract

1. Exposed riverine sediments are difficult substrata for seedling establishment because of extremes in the microclimate, poor soil conditions and frequent habitat turnover. Various species of willows and poplars (Salicaceae) appear to be particularly successful in colonising such sediments and are often dominant in floodplain habitats throughout the northern temperate zone. 2. In many Salicaceae regeneration seems to be adapted to regular disturbance by flooding. Efficient seed dispersal is achieved by the production of abundant seed in spring and early summer, which are dispersed by air and water. Seeds are short‐lived and germinate immediately on moist surfaces. Seedling establishment is only possible if these surfaces stay moist and undisturbed for a sufficient period of time. 3. Larger plants of Salicaceae have exceptional mechanical properties, such as high bending stability, which enable them to withstand moderate floods. If uprooted, washed away or fragmented by more powerful floods these plants re‐sprout vigorously. 4. While these life characteristics can be interpreted as adaptations to the floodplain environment, they may also cause a high genetic variability in populations of Salicaceae and predispose Salicaceae to hybridization. Thus, a feed back between adaptive life history characteristics and the evolutionary process is proposed.

Admixture in European Populus hybrid zones makes feasible the mapping of loci that contribute to reproductive isolation and trait differences

“…P. alba and P. tremula exhibit several features that render them potentially suitable for admixture mapping of detrimental or adaptive trait variation. Firstly, they are ecologically divergent: P. alba is restricted mainly to lowland flood-plain forests whereas P. tremula occurs in mixed upland communities (Adler et al, 1994), and traits potentially involved in these divergent ecological preferences have been identified (Karrenberg et al, 2002). Second, species barriers in Populus are likely to be genic rather than chromosomal (Cervera et al, 2001;Lexer et al, 2005), and thus variation at genic factors involved in species isolation should segregate in hybrids.…”

Encroachment of upland Mediterranean plant species in riparian ecosystems of southern Portugal

“…Blackberry shrubs are probably the most related to the observed positive influence on riparian richness, since they are the ones most detected. Blackberry shrubs tend to create a very dense canopy, which may prevent light from reaching the riparian species seeds; however, willows and poplar seeds are known to germinate in the dark (Karrenberg et al 2002). Thus, blackberry bushes may facilitate the germination seeds from these species, which occurs in a short period (a few days), and also prevent seed mortality from desiccation by providing shade (Karrenberg et al 2002).…”

The obscure events contributing to the evolution of an incipient sex chromosome in Populus: a retrospective working hypothesis

“…Only about 4 % of higher plants are dioecious (Ainsworth 2000;Ming et al 2007;Heslop-Harrison and Schwarzacher 2011). This reproductive habit in Populus, along with the ubiquitous vegetative reproduction via root suckering, air layering, and/or cladoptosis, evolved proximally to or simultaneously with the advent of this family 65 million years ago, as nearly all members of the Salicaceae family displays these habits (Karrenberg et al 2002;Eckenwalder 1996). Dioecy in Populus is strongly genetically controlled, and a region of the genome located on chromosome XIX appears to contain a gene (genes) that controls gender determination, though there are noted examples of gender reversion and hermaphroditic plants in most species (Rottenberg et al 2000;Markussen et al 2007;Gaudet et al 2008;Pakull et al 2009Pakull et al , 2011Paolucci et al 2010).…”