[Coral-List] Sponge defenses and community organization: New publication

[Janie Wulff]

Dear Friends and Colleagues,

I'm excited to share with you a new publication:  Targeted predator 
defenses of sponges shape community organization and tropical marine 
ecosystem function. Wulff, J.L. 2020./Ecological Monograp/hs 
00(00):e01438. 10.1002/ecm.1438


The featured data set, collected in the field over 20 years, encourages 
reinterpretation of several controversial patterns and processes in 
coral reef, seagrass meadow, and mangrove ecosystems. The Abstract is 
pasted below. If you don't have ready access to Ecological Society of 
America publications, I invite you to send me an email and I’ll respond 
with a pdf.


Best wishes!
Janie

Here’s the ABSTRACT:

Defenses that target particular consumers often influence community 
organization, ecosystem function, and diversity maintenance. In coral 
reef, mangrove, and seagrass ecosystems, sponges affect substratum 
stability, water clarity, diversity of associated species, and survival 
of habitat-providing organisms, key roles not duplicated by other 
organisms. Whether and how predators control sponges are much disputed. 
Substantial ecosystem consequences of losing or gaining sponges 
motivated definitive experiments on how predators control sponge 
distribution and abundance. Caribbean sponges of 94 species representing 
13 taxonomic orders and three linked habitats (coral reefs, mangroves, 
and seagrass meadows) were exposed to seven predator species 
representing different habitats and degrees of spongivory in 4493 in 
situ//trials. The resulting data force reassessment of popular 
interpretations of several patterns and processes. Contrary to extract 
pellet assays that declare most sponges deterrent, 78% of these 94 
species were eaten by at least one predator. But “palatability” is 
consumer dependent: a sponge species eaten by one predator can be 
rejected by other predators, and predator species differed in what 
sponges they ate in 55.4% (214/392) of pairwise comparisons between 
predators. Because spongivore species are usually restricted to 
particular habitats, they impose abrupt boundaries on sponges’ habitat 
distributions, reflecting inverse relationships between accessibility 
and palatability to each predator. Thus a seagrass-dwelling starfish 
eats only 9% of seagrass sponge species, but 70% of coral reef species, 
and 78% of mangrove species. Reef-dwelling angelfishes completely 
consume only 13% of reef species, but 29% of seagrass species, and 63% 
of mangrove species. Defenses that target specific predators reveal that 
spongivore influence on community organization cannot be inferred from 
extract pellet/omnivore assays that assume defenses target all predators 
equally. In fact, pellet data wrongly predicted actual consumption of 
living sponges of that pellet's species in 43% of field experiments with 
spongivores. In contrast with herbivore-plant interactions, 
opportunistic spongivory is at least as important as routine spongivory 
for community organization and ecosystem function. Potential for loss of 
key functional roles of sponges, if opportunistic predators gain access 
to sponge species that lack defenses against them, must inform 
conservation plans for coral reef, mangrove, and seagrass ecosystems.

**