Reduced fecundity and offspring performance in small populations of the declining grassland plantsPrimula verisandGentiana lutea

Abstract

Summary 1We studied reproduction and o spring performance in relation to population size in the declining self-incompatible perennials Primula veris and Gentiana lutea. In both species, reproduction was strongly reduced in small populations, where plants produced fewer seeds per fruit and per plant. Total seed mass per plant was higher in large populations, but individual seeds were smaller, indicating a tradeo between seed number and size. Reproduction was depressed most strongly in populations consisting of less than c. 200 (P. veris) and c. 500 plants (G. lutea), respectively. 2 The inclusion of plant size (an integrated measure of habitat quality) in the statistical models did not change the relationships between fecundity and population size. Pollen limitation or inbreeding depression in small populations are therefore more likely explanations for these patterns than is habitat quality. 3 Germination rate and survival of seedlings in a common environment was not related to population size in either species, although P. veris developed into larger rosettes when seeds were derived from large populations. This suggests that inbreeding depression occurs in small populations of P. veris. 4 In a factorial fertilizer-by-competition experiment with P. veris, o spring from larger populations grew signi®cantly larger and responded more strongly to fertilizer. For this declining species genetic deterioration as a result of habitat fragmentation may therefore aggravate the e ects of environmental changes such as habitat eutrophication. 5 Our results suggest that small populations may face an increased short-term risk of extinction because of reduced reproduction, and an increased long-term risk because they are less able to respond to environmental changes.

Effect of population size on the prospect of species survival

“…This is supported by the high variation of these traits in this dataset and has been repeatedly suggested by others (e.g. KÉRY et al 2000, LOISON et al 2001, PASCHKE et al 2002, VERGEER et al 2003. However data on survival of adult individuals (i.e., on transitions with the highest elasticity) in populations of different sizes are lacking, and their importance thus still remains an open issue for future studies (but see similar test by OLI 2003).…”

“…MENGES 1991, RAIJMANN et al 1994, HESCHEL & PAIGE 1995, KÉRY et al 2000, FISCHER et al 2000. The absence of this relationship in the data on seed production per plant shows that the conclusion of the no relationship studies (e.g.…”

Genetic rescue in interconnected populations of small and large size of the self-incompatible Ranunculus reptans

“…Numerous studies of plants (and animals) have recorded reduced fitness in small populations in nature and when individuals from small populations are raised in a common environment (Menges, 1991;Oostermeijer et al, 1994;Heschel and Paige, 1995;Fischer and Matthies, 1998;Morgan, 1999;Fischer et al, 2000a;Kéry et al, 2000;Luijten et al, 2000;Schmidt and Jensen, 2000;Mavraganis and Eckert, 2001;Jacquemyn et al, 2002;Paschke et al, 2002;Severns, 2003;Vergeer et al, 2003;Brys et al, 2004). There are three likely genetic causes for reduced fitness of plants from smaller populations.…”

Natural Fecundity and Germination Characteristics of Selected Cyclopia (Honeybush) Species: Preliminary Findings

“…Thereafter, seeds from each inflorescence were randomly weighed to determine the mass of each seed lot per inflorescence. The mean seed mass was calculated by dividing the mass of harvested seeds by the number of counted seeds, since using threshold of seed mass per 100 seeds was not feasible due to that some genotypes plants produced far less number of seeds (Kéry et al, 2000). Lastly, the total number of seeds per individual plant was calculated as the total seed mass per plant divided by the mean seed mass (Snow et al, 2003;Dainese, 2011).…”

“…As resource availability allows in favourable periods, fruits of highest quality are matured and the remainder aborted (Lee & Bazzaz, 1982;Teixera, Pareira, & Ranga, 2006;Dao, Diallo, & Kabore-Zoungrana, 2012). Differences in Cyclopia intra-and inter-species pod development and filling can be due to resource accrual and partitioning during seed development among plants within the same growing season (Kéry et al, 2000;Carrió, Jiménez, Sánchez-Gómez, & Güemes, 2009;Valtueña et al, 2010). Therefore, genotypic differences in utilisation of photoassimilates or other nutrients which are reliant on the timing and duration of phenology, physiological constraints, climatic conditions and maternal effects can affect reproductive fitness in the Cyclopia species.…”