Predators selectively graze reproductive structures in a clonal marine organism
- PDF / 354,218 Bytes
- 9 Pages / 595.276 x 790.866 pts Page_size
- 105 Downloads / 205 Views
ORIGINAL PAPER
Predators selectively graze reproductive structures in a clonal marine organism Randi D. Rotjan Æ Sara M. Lewis
Received: 13 April 2008 / Accepted: 1 December 2008 / Published online: 23 December 2008 Ó Springer-Verlag 2008
Abstract Although the fitness consequences of herbivory on terrestrial plants have been extensively studied, considerably less is known about how partial predation impacts the fitness of clonal marine organisms. The trophic role of Caribbean parrotfish on coral reefs is complex: while these fish are important herbivores, as corallivores (consumers of live coral tissue), they selectively graze specific species and colonies of reef-building corals. Though the benefits of parrotfish herbivory for reef resilience and conservation are well documented, the negative consequences of parrotfish grazing for coral reproductive fitness have not been previously determined. We examined recently grazed colonies of Montastraea annularis corals to determine whether grazing was positively associated with coral reproductive effort. We measured gonad number, egg number and size, and proportional reproductive allocation for grazed and intact coral colonies 2–5 days prior to their annual spawning time. We found that parrotfish selectively grazed coral polyps with high total reproductive effort (number of gonads), providing the first evidence that parrotfish selectively target specific tissue areas within a single coral colony. The removal of polyps with high reproductive effort has direct adverse affects on coral fitness, with additional indirect implications for colony growth and survival. We conclude that chronic grazing by parrotfishes
Communicated by M. Byrne. R. D. Rotjan S. M. Lewis Department of Biology, Tufts University, Medford, MA 02155, USA R. D. Rotjan (&) Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA e-mail: [email protected]; [email protected]
has negative fitness consequences for reef-building corals, and by extension, reef ecosystems.
Introduction Herbivory has been intensively studied in terrestrial and marine ecosystems, and it is well known that herbivores have numerous and diverse impacts on plant fitness, community structure and ecosystem function (e.g. Lubchenco and Gaines 1981; Fritz and Simms 1992). For example, consumption of floral tissue has adverse impacts on terrestrial plant reproduction (reviewed by McCall and Irwin 2006) by directly limiting gamete production and dispersal (e.g. Louda and Potvin 1995; Krupnick and Weis 1999), as well as indirectly reducing plant fitness via reduced pollination success (e.g. Krupnick and Weis 1999; Leavitt and Robertson 2006). In clonal plants, reproductive consequences of florivory are known to include reduced seed production and increased clonal growth (e.g. Tobler et al. 2006). Furthermore, foliar herbivory (leaf damage and removal) has also been shown to negatively impact plant fitness (e.g. Wisdom et al. 1989; Avila-Sakar and Stephenson 2006). However, despite our extensive knowled
Data Loading...
