Limits...
Stage-dependent responses to emergent habitat heterogeneity: consequences for a predatory insect population in a coffee agroecosystem.

Liere H, Perfecto I, Vandermeer J - Ecol Evol (2014)

Bottom Line: Interactions among members of biological communities can create spatial patterns that effectively generate habitat heterogeneity for other members in the community, and this heterogeneity might be crucial for their persistence.The abundance of adult beetles located around trees with ants increased with the size of the ant nest clusters but the relationship is not significant for larvae.We suggest that this dependency arises due to the different responses that the predator's life stages have to this emergent spatial pattern.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of the South 735 University Ave, Sewanee, Tennessee, 37383.

ABSTRACT
Interactions among members of biological communities can create spatial patterns that effectively generate habitat heterogeneity for other members in the community, and this heterogeneity might be crucial for their persistence. For example, stage-dependent vulnerability of a predatory lady beetle to aggression of the ant, Azteca instabilis, creates two habitat types that are utilized differently by the immature and adult life stages of the beetle. Due to a mutualistic association between A. instabilis and the hemipteran Coccus viridis - which is A. orbigera main prey in the area - only plants around ant nests have high C. viridis populations. Here, we report on a series of surveys at three different scales aimed at detecting how the presence and clustered distribution of ant nests affect the distribution of the different life stages of this predatory lady beetle in a coffee farm in Chiapas, Mexico. Both beetle adults and larvae were more abundant in areas with ant nests, but adults were restricted to the peripheries of highest ant activity and outside the reach of coffee bushes containing the highest densities of lady beetle larvae. The abundance of adult beetles located around trees with ants increased with the size of the ant nest clusters but the relationship is not significant for larvae. Thus, we suggest that A. orbigera undergoes an ontogenetic niche shift, not through shifting prey species, but through stage-specific vulnerability differences against a competitor that renders areas of abundant prey populations inaccessible for adults but not for larvae. Together with evidence presented elsewhere, this study shows how an important predator is not only dependent on the existence of two qualitatively distinct habitat types, but also on the spatial distribution of these habitats. We suggest that this dependency arises due to the different responses that the predator's life stages have to this emergent spatial pattern.

No MeSH data available.


Related in: MedlinePlus

Map of a 45-ha permanent plot in a coffee farm in Mexico showing Azya orbigera abundance distribution in relation to Azteca instabilis nests. Red dots represent A. instabilis nests, and gray-scaled squares represent beetle adult (left panel) and larvae (right panel) abundance in coffee bushes within a 5 m radius of the sampled tree. White squares represent zeroes, light gray squares represent low abundances, and dark gray squares represent high abundances (adults: min = 0, max = 43; larvae min = 0, max = 56). One tree per 50 × 50 m quadrant was sampled. The maps show the sampling of rainy season, 2006.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4222207&req=5

fig02: Map of a 45-ha permanent plot in a coffee farm in Mexico showing Azya orbigera abundance distribution in relation to Azteca instabilis nests. Red dots represent A. instabilis nests, and gray-scaled squares represent beetle adult (left panel) and larvae (right panel) abundance in coffee bushes within a 5 m radius of the sampled tree. White squares represent zeroes, light gray squares represent low abundances, and dark gray squares represent high abundances (adults: min = 0, max = 43; larvae min = 0, max = 56). One tree per 50 × 50 m quadrant was sampled. The maps show the sampling of rainy season, 2006.

Mentions: Figure 2 shows the spatial distribution of ant nests and adult and larval beetle abundance during the rainy season of the first sampling year. We found that a GLMM with a random intercept and slope terms for site, year, and season, significantly reduced the AIC values (Table 1). Mean adult abundance increased from 0.4 individuals per focal tree (ind/tree) in areas without ants to 3.3 ind/tree in areas with ants, while mean larvae abundance increased from 0.4 ind/tree in areas without ants to 1.4 ind/tree in areas with ants (GLMM results: Tables 1, 2, 3). Ant nest density at 20 m had a significant positive effect on adult abundances but a negative albeit nonsignificant one on larvae abundance (Table 2). Ant nest density at 50 m was not present in the best models for adults or for larvae. The pseudo-R2 (estimated with a Spearman correlation of the fitted vs. observed values) was 0.51 for adults and for larvae 0.38.


Stage-dependent responses to emergent habitat heterogeneity: consequences for a predatory insect population in a coffee agroecosystem.

Liere H, Perfecto I, Vandermeer J - Ecol Evol (2014)

Map of a 45-ha permanent plot in a coffee farm in Mexico showing Azya orbigera abundance distribution in relation to Azteca instabilis nests. Red dots represent A. instabilis nests, and gray-scaled squares represent beetle adult (left panel) and larvae (right panel) abundance in coffee bushes within a 5 m radius of the sampled tree. White squares represent zeroes, light gray squares represent low abundances, and dark gray squares represent high abundances (adults: min = 0, max = 43; larvae min = 0, max = 56). One tree per 50 × 50 m quadrant was sampled. The maps show the sampling of rainy season, 2006.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4222207&req=5

fig02: Map of a 45-ha permanent plot in a coffee farm in Mexico showing Azya orbigera abundance distribution in relation to Azteca instabilis nests. Red dots represent A. instabilis nests, and gray-scaled squares represent beetle adult (left panel) and larvae (right panel) abundance in coffee bushes within a 5 m radius of the sampled tree. White squares represent zeroes, light gray squares represent low abundances, and dark gray squares represent high abundances (adults: min = 0, max = 43; larvae min = 0, max = 56). One tree per 50 × 50 m quadrant was sampled. The maps show the sampling of rainy season, 2006.
Mentions: Figure 2 shows the spatial distribution of ant nests and adult and larval beetle abundance during the rainy season of the first sampling year. We found that a GLMM with a random intercept and slope terms for site, year, and season, significantly reduced the AIC values (Table 1). Mean adult abundance increased from 0.4 individuals per focal tree (ind/tree) in areas without ants to 3.3 ind/tree in areas with ants, while mean larvae abundance increased from 0.4 ind/tree in areas without ants to 1.4 ind/tree in areas with ants (GLMM results: Tables 1, 2, 3). Ant nest density at 20 m had a significant positive effect on adult abundances but a negative albeit nonsignificant one on larvae abundance (Table 2). Ant nest density at 50 m was not present in the best models for adults or for larvae. The pseudo-R2 (estimated with a Spearman correlation of the fitted vs. observed values) was 0.51 for adults and for larvae 0.38.

Bottom Line: Interactions among members of biological communities can create spatial patterns that effectively generate habitat heterogeneity for other members in the community, and this heterogeneity might be crucial for their persistence.The abundance of adult beetles located around trees with ants increased with the size of the ant nest clusters but the relationship is not significant for larvae.We suggest that this dependency arises due to the different responses that the predator's life stages have to this emergent spatial pattern.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of the South 735 University Ave, Sewanee, Tennessee, 37383.

ABSTRACT
Interactions among members of biological communities can create spatial patterns that effectively generate habitat heterogeneity for other members in the community, and this heterogeneity might be crucial for their persistence. For example, stage-dependent vulnerability of a predatory lady beetle to aggression of the ant, Azteca instabilis, creates two habitat types that are utilized differently by the immature and adult life stages of the beetle. Due to a mutualistic association between A. instabilis and the hemipteran Coccus viridis - which is A. orbigera main prey in the area - only plants around ant nests have high C. viridis populations. Here, we report on a series of surveys at three different scales aimed at detecting how the presence and clustered distribution of ant nests affect the distribution of the different life stages of this predatory lady beetle in a coffee farm in Chiapas, Mexico. Both beetle adults and larvae were more abundant in areas with ant nests, but adults were restricted to the peripheries of highest ant activity and outside the reach of coffee bushes containing the highest densities of lady beetle larvae. The abundance of adult beetles located around trees with ants increased with the size of the ant nest clusters but the relationship is not significant for larvae. Thus, we suggest that A. orbigera undergoes an ontogenetic niche shift, not through shifting prey species, but through stage-specific vulnerability differences against a competitor that renders areas of abundant prey populations inaccessible for adults but not for larvae. Together with evidence presented elsewhere, this study shows how an important predator is not only dependent on the existence of two qualitatively distinct habitat types, but also on the spatial distribution of these habitats. We suggest that this dependency arises due to the different responses that the predator's life stages have to this emergent spatial pattern.

No MeSH data available.


Related in: MedlinePlus