Abstract
The Janzen-Connell hypothesis states that tree diversity in tropical forests is maintained by specialist predators that are distance- or density-responsive (i.e. predators that reduce seed or seedling survival near adults of their hosts). Many empirical studies have investigated whether predators are distance-responsive; however, few studies have examined whether distance-responsiveness matters for how predators maintain tree diversity. Using a site-occupancy model, we show analytically that distance-responsive predators are actually less able to maintain diversity than specialist predators that are not distance-responsive. Generally, specialist predators maintain diversity because they become rare when their host's densities are low, reducing predation risk. However, if predators are distance-responsive, and most seeds cannot disperse away from these predators, then seed predation rates will remain high, even if predator density is low across the landscape. Consequently, a reduction in a host's population density may not lead to a significant reduction in seed and seedling predation. We show that habitat partitioning can cause recruitment to be highest near conspecific adults, even in the presence of distance-responsive predators, without any change in the effect that the predators have on coexistence (a result contrary to predictions of the Janzen-Connell hypothesis). Rather, specialist predators and habitat partitioning have additive effects on species coexistence in our model, i.e., neither mechanism alters the effect of the other one.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 60-70 |
| Number of pages | 11 |
| Journal | Theoretical Population Biology |
| Volume | 106 |
| DOIs | |
| State | Published - Dec 1 2015 |
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Keywords
- Coexistence
- Fitness-density covariance
- Habitat partitioning
- Janzen-Connell hypothesis
- Predator partitioning
- Spatial storage effect
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
Cite this
Distance-responsive predation is not necessary for the Janzen-Connell hypothesis. / Stump, Simon Maccracken; Chesson, Peter.
In: Theoretical Population Biology, Vol. 106, 01.12.2015, p. 60-70.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Distance-responsive predation is not necessary for the Janzen-Connell hypothesis
AU - Stump, Simon Maccracken
AU - Chesson, Peter
PY - 2015/12/1
Y1 - 2015/12/1
N2 - The Janzen-Connell hypothesis states that tree diversity in tropical forests is maintained by specialist predators that are distance- or density-responsive (i.e. predators that reduce seed or seedling survival near adults of their hosts). Many empirical studies have investigated whether predators are distance-responsive; however, few studies have examined whether distance-responsiveness matters for how predators maintain tree diversity. Using a site-occupancy model, we show analytically that distance-responsive predators are actually less able to maintain diversity than specialist predators that are not distance-responsive. Generally, specialist predators maintain diversity because they become rare when their host's densities are low, reducing predation risk. However, if predators are distance-responsive, and most seeds cannot disperse away from these predators, then seed predation rates will remain high, even if predator density is low across the landscape. Consequently, a reduction in a host's population density may not lead to a significant reduction in seed and seedling predation. We show that habitat partitioning can cause recruitment to be highest near conspecific adults, even in the presence of distance-responsive predators, without any change in the effect that the predators have on coexistence (a result contrary to predictions of the Janzen-Connell hypothesis). Rather, specialist predators and habitat partitioning have additive effects on species coexistence in our model, i.e., neither mechanism alters the effect of the other one.
AB - The Janzen-Connell hypothesis states that tree diversity in tropical forests is maintained by specialist predators that are distance- or density-responsive (i.e. predators that reduce seed or seedling survival near adults of their hosts). Many empirical studies have investigated whether predators are distance-responsive; however, few studies have examined whether distance-responsiveness matters for how predators maintain tree diversity. Using a site-occupancy model, we show analytically that distance-responsive predators are actually less able to maintain diversity than specialist predators that are not distance-responsive. Generally, specialist predators maintain diversity because they become rare when their host's densities are low, reducing predation risk. However, if predators are distance-responsive, and most seeds cannot disperse away from these predators, then seed predation rates will remain high, even if predator density is low across the landscape. Consequently, a reduction in a host's population density may not lead to a significant reduction in seed and seedling predation. We show that habitat partitioning can cause recruitment to be highest near conspecific adults, even in the presence of distance-responsive predators, without any change in the effect that the predators have on coexistence (a result contrary to predictions of the Janzen-Connell hypothesis). Rather, specialist predators and habitat partitioning have additive effects on species coexistence in our model, i.e., neither mechanism alters the effect of the other one.
KW - Coexistence
KW - Fitness-density covariance
KW - Habitat partitioning
KW - Janzen-Connell hypothesis
KW - Predator partitioning
KW - Spatial storage effect
UR - http://www.scopus.com/inward/record.url?scp=84959557324&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84959557324&partnerID=8YFLogxK
U2 - 10.1016/j.tpb.2015.10.006
DO - 10.1016/j.tpb.2015.10.006
M3 - Article
C2 - 26525355
AN - SCOPUS:84959557324
VL - 106
SP - 60
EP - 70
JO - Theoretical Population Biology
JF - Theoretical Population Biology
SN - 0040-5809
ER -