Secondary removal ofMyristica fatua(Myristicaceae) seeds by crabs inMyristicaswamp forests in India

Abstract

Little is known about the role of crabs as seed dispersers and predators. Recently, there has been interest in understanding their influence on plant recruitment in coastal forests. Secondary seed removal by crabs in a swampspecialist tree, Myristica fatua, was investigated in the rare and patchy freshwater Myristica swamps in the Western Ghats in India. Tethered-line experiments were used to determine the role of crabs as secondary seed-removal agents in two study sites. Crabs transported a large percentage (63.3%) of seeds (n = 60) placed on the forest floor compared with rodents (25%) and other unknown agents (13.3%). Simultaneous choice experiments suggested that the nutrient-rich arils covering seeds were consumed, but there was no evidence for seed predation by crabs. A small percentage (13.3%) of monitored seeds (n = 60) germinated from within crab burrows. The spatial scale of secondary removal by crabs was restricted to < 10 m. In these fragmented swamp forests, secondary removal by crabs retains seeds largely within the swamps, where conditions for their establishment and survival are optimal. Thus, secondary seed removal by crabs could provide temporal and spatial refugia from seed predators such as rodents in Myristica fatua.

Low redundancy in seed dispersal within an island frugivore community

“…2003 ; Shiels and Drake 2011 ). Crabs were more likely than rats to disperse seeds ( Lee 1985 ; Krishna and Somanathan 2014 ), but still destroyed seeds of three of the seven species we identified as crab-consumed. However, partial consumption of a seed's cotyledons does not always result in seed death.…”

“…Even local dispersal events are dominated by flying foxes in our study system. Crabs move fruits away from the source to avoid competition with other crabs ( Lee 1985 ), and whereas distances are <10 m from parent crowns, they may leave seeds in burrows where the seed is protected from rodent predation ( Lee 1985 ; Krishna and Somanathan 2014 ). Similarly, rats carry seeds to areas nearby where they can be sheltered from predators while feeding ( McConkey et al .…”

Spatiotemporal strategies that facilitate recruitment in a habitat specialist tree species

“…However, in our study, secondary agents evenly removed seeds in all microsite types (>90 % of total seeds in seed stations). The localized dispersal by crabs (mean distance = 1.89 m) into or close to burrows to consume the arils can preclude seed predation by other agents as well as retain seeds within the swamp habitat without substantially altering the initial spatial pattern of seed deposition ( Krishna and Somanathan 2014 ).…”

“…In our previous study, we found that secondarily removed seeds met with mixed fates in which crabs secondarily removed >60 % of M. fatua seeds (moved seeds into burrows which facilitated escape from predation), while 25 % of the seeds were subjected to predation by rodents and squirrels or weevil infestation (1 %) ( Krishna and Somanathan 2014 ).…”

Phytosociological Analysis of <i>Myristica</i> Swamp Forests of Kulathupuzha, Kerala, India

“…These swamps are dominated by trees of the Myristicaceae family which is placed along with other 'living fossil' families of primitive dicots like Magnoliaceae, Annonaceae and Chloranthaceae 19 . These swamps are also a site for unique plant-animal interactions such as pollination 20,21 and secondary seed removal 22 . The swamps are characterized by high endemism 23 of up to 61.11% (ref.…”