Interactions of inbreeding and stress by poor host quality in a root hemiparasite

Abstract

Background and Aims Populations of many hemiparasitic plants are fragmented and threatened by inbreeding depression (ID). In addition, they may also be strongly affected by a lack of suitable host species. However, nothing is known about possible interactive effects of inbreeding and host quality for parasitic plants. Poor host quality represents a special type of biotic stress and the magnitude of ID is often expected to be higher in more stressful environments.Methods We studied the effects of inbreeding and the quality of host species for the declining root hemiparasite Rhinanthus alectorolophus. Selfed and open-pollinated parasites from two natural populations were grown (1) with 13 potential host species and (2) with 15 four-species mixtures.Key Results ID differed among host species and mixtures. In the first experiment, ID was highest in parasites grown with good hosts and declined with stress intensity. In the second experiment, ID was not influenced by stress intensity, but was highest in mixtures of hosts from only one functional group and lowest in mixtures containing three functional groups. Both parasite performance with individual host species and the damage to these host species differed between parasites from the two study populations.Conclusions Our results contradict the common assumption that ID is generally higher in more stressful environments. In addition, they support the importance of diverse host communities for hemiparasitic plants. The differences in host quality between the two parasite populations indicate genetic variation in the adaptation to individual hosts and in host-specific virulence. However, inbreeding did not affect specific host-parasite interactions.

Responses of a legume to inbreeding and the intensity of novel and familiar stresses

“…This justifies the expectation that if a general relationship between ID and stress intensity exists, ID should also increase in A. vulneraria in response to our stress treatments, which was not the case. Our findings are in line with those of other recent studies that investigated ID in individual species under several stresses of different intensity using Drosophila melanogaster (Yun & Agrawal, ), S. vulgaris (Sandner & Matthies, ) and Rhinanthus alectorolophus (Sandner & Matthies, ). There is thus little support for a linear increase of ID with stress intensity irrespective of the type of stress.…”

“…The phenotypic variation (CV 2 ) in biomass was highest under waterlogging and lowest under drought, but ID was not related to differences in CV 2 or size depression. Similarly, in the hemiparasite R. alectorolophus , the CV 2 of plants grown with different host species was independent of stress intensity and ID (Sandner & Matthies, ). In contrast, in animal studies, stress intensity, phenotypic variation, and ID were correlated (Long et al, ; Reed et al, ).…”

Evaluating the efficacy of independent versus simultaneous management strategies to address ecological and genetic threats to population viability

“…Specifically, inbreeding depression would be negligible in very harsh environments where all individuals perform poorly, and actually increase as environmental quality, and hence the opportunity for variation in fitness, increases (Figure ). Such weak inbreeding depression in very harsh experimental environments was observed in Brassica rapa (Waller et al, ) and Rhinanthus alectorolophus (Sandner & Matthies, ), and may explain inconsistent environmental effects on inbreeding depression in Soay sheep ( Ovis aries, Pemberton, Ellis, Pilkington, & Bérénos, ). Translocations to reduce inbreeding may then provide little improvement in population viability and instead waste conservation resources.…”

Genetic Diversity and Structure in the Philippine Rafflesia lagascae Complex (Rafflesiaceae) inform its Taxonomic Delimitation and Conservation

“…The host species of parasitic plants form essential components of their environment (Sandner and Matthies 2017). Their distribution patterns constitute the maximum potential distribution area of the parasitic plant species that depend on them for their existence (Costea and Stefanović 2009) in the same way that specialists of a rare habitat are confined to areas where this habitat is found (e.g.…”

“…This might ultimately result in a loss of genetic diversity and thereby increase the probability that small and isolated populations go extinct (Schmidt and Jensen 2000). Indeed, many parasitic plant species are rare and listed as threatened or endangered (Marvier and Smith 1997;Sandner and Matthies 2017). Parasitic species that are very host specific are especially at risk, because they are particularly sensitive to changes in host availability and typically have small distribution areas (Costea and Stefanović 2009).…”