TY  - JOUR
A1  - Nottebrock, Henning
A1  - Esler, Karen J.
A1  - Schurr, Frank Martin
T1  - Effects of intraspecific and community density on the lifetime fecundity of long-lived shrubs
JF  - Perspectives in plant ecology, evolution and systematics
N2  - Intra- and interspecific density dependence has profound consequences for plant population and community dynamics. In long-lived plants, however, lifetime patterns and mechanisms of density dependence are difficult to study. Here, we examine effects of intraspecific and community density on the lifetime fecundity of two long-lived shrub species from South African Fynbos: Protea repens (animal-pollinated, hermaphroditic) and Leucadendron rubrum (wind-pollinated, dioecious). Both species are serotinous, retaining seeds in cones until fire kills the mother plant. We measured lifetime fecundity as the product of cone number, proportion of cones that are not damaged by predation and seed set (fertile seeds per intact cone). Intraspecific and community densities were quantified by counting individuals of target species and all Proteaceae in small- and large-scale neighbourhoods (10 m and 50 m radius) around each focal individual. Additionally, we determined the age and size of focal individuals. We found that lifetime fecundity of the wind-pollinated L rubrum is density independent. In contrast, the lifetime fecundity of the animal-pollinated P. repens increases with large-scale intraspecific density and shows a hump-shaped relationship to large-scale community density. Community density has a hump-shaped effect on seed set (probably through partial absence of generalized pollinators at low and competition for pollinators at high densities) and negatively affects cone number per individual. For both species, plant age decreases seed set while increasing lifetime fecundity. The qualitative differences in the density dependence of lifetime fecundity may arise from differences between animal and wind pollination. In particular, interactions with generalized animal pollinators may cause community-level Allee effects with profound consequences for the future dynamics of long-lived plant populations and communities.
KW  - Competition
KW  - Community-level Allee effects
KW  - Facilitation
KW  - Fitness components
KW  - Interspecific interactions
KW  - Plant-animal interactions
Y1  - 2013
U6  - https://doi.org/10.1016/j.ppees.2013.03.003
SN  - 1433-8319
VL  - 15
IS  - 3
SP  - 150
EP  - 161
PB  - Elsevier
CY  - Jena
ER  - 
TY  - JOUR
A1  - Braga, Raul Renno
A1  - Gomez-Aparicio, Lorena
A1  - Heger, Tina
A1  - Simoes Vitule, Jean Ricardo
A1  - Jeschke, Jonathan M.
T1  - Structuring evidence for invasional meltdown
BT  - broad support but with biases and gaps
JF  - Biological invasions : unique international journal uniting scientists in the broad field of biological invasions
N2  - Negative interactions have been suggested as a major barrier for species arriving in a new habitat. More recently, positive interactions drew attention from community assembly theory and invasion science. The invasional meltdown hypothesis (IMH) introduced the idea that positive interactions among non-native species could facilitate one another’s invasion, even increasing their impact upon the native community. Many studies have addressed IMH, but with contrasting results, reflecting various types of evidence on a multitude of scales. Here we use the hierarchy-of-hypotheses (HoH) approach to differentiate key aspects of IMH, organizing and linking empirical studies to sub-hypotheses of IMH. We also assess the level of empirical support for each sub-hypothesis based on the evidence reported in the studies. We identified 150 studies addressing IMH. The majority of studies support IMH, but the evidence comes from studies with different aims and questions. Supporting studies at the community or ecosystem level are currently rare. Evidence is scarce for marine habitats and vertebrates. Few sub-hypotheses are questioned by more than 50% of the evaluated studies, indicating that non-native species do not affect each other’s survival, growth, reproduction, abundance, density or biomass in reciprocal A ↔ B interactions. With the HoH for IMH presented here, we can monitor progress in empirical tests and evidences of IMH. For instance, more tests at the community and ecosystem level are needed, as these are necessary to address the core of this hypothesis.
KW  - Facilitation
KW  - Mutualism
KW  - Review
KW  - Nonindigenous
KW  - Exotic
Y1  - 2018
U6  - https://doi.org/10.1007/s10530-017-1582-2
SN  - 1387-3547
SN  - 1573-1464
VL  - 20
IS  - 4
SP  - 923
EP  - 936
PB  - Springer
CY  - Dordrecht
ER  -