Andrew L. Mack

Did fleshy fruit pulp evolve as a defence against seed loss rather than as a dispersal mechanism

Relatively few studies have examined the evolution of the mutualism between endozoochorous plants and seed dispersers. Most seed dispersal studies are ecological and examine the role offruit pulp in promoting seed dispersal. This interaction is often assumed to have originated due to selection stemming from seed dispersers. Here I suggest a “defence scenario” wherein fleshy fruits originated as mechanisms to defend seeds and secondarily became structures to promote seed dispersal. I suggest that frugivory followed from herbivores that specialized on consuming seed defensive tissues and that enhanced seed dispersal was initially a consequence of seed defence. The proposed defence scenario is not posited as an explanation for the sequence that led to all modern frugivores. However, it is suggested that seed predation was the initial source of selection that led to fleshy fruits; the necessary precursor to frugivory. Support is described from the fossil record and from modern structures and interactions. Testable predictions are made in hope that greater interest will be focused on the defensive role of fleshy fruit pulp both in modern interactions and historically.

LOW-FREQUENCY VOCALIZATIONS BY CASSOWARIES (CASUARIUS SPP.)

Abstract Although some birds can detect wavelengths in the infrasound range, there has been litle evidence that birds produce very low frequencies. We made nine recordings of a captive Dwarf Cassowary (Casuarius benneti) and one recording of a wild Southern Cassowary (C. casuarius) near Crater Mountain, Papua New Guinea. Both species produced sounds near the floor of the human hearing range in their pulsed booming notes: down to 32 Hz for C. casuarius and 23 Hz in C. benneti. Recordings of C. benneti indicate four levels of harmonics with the 23 Hz fundamental frequency. Such low frequencies are probably ideal for communication among widely dispersed, solitary cassowaries in dense rainforest. The discovery of very low-frequency communication by cassowaries creates new possibilities for studying those extremely secretive birds and for learning more about the evolution of avian vocalizations.

A non-intrusive method for measuring movements and seed dispersal in cassowaries

Abstract We describe a method for measuring gut passage time and seed dispersal distance for a large terrestrial frugivore. We attached temperature data loggers to radio transmitters in baits that were ingested by free-ranging cassowaries. The resulting data yielded information on how fast the unit passed through the gut (3–4 h) and how far they were moved (240–325 m), an analog for dispersed seeds. Additionally, the data loggers revealed that cassowaries reingest fecal matter, the first observation of coprophagy in wild cassowaries.

The Frugivore Community and the Fruiting Plant Flora in a New Guinea Rainforest: Identifying Keystone Frugivores

The flora at Crater Mountain Biological Research Station in Papua New Guinea is very diverse: 228 tree species ( 10 cm DBH) on a single hectare. However, the vertebrate fauna (169 bird and 31 mammal species) is less diverse than many tropical sites. At least 47% of bird species and 29% of mammal species are partially frugivorous. Using data on relative abundance, mass, and degree of frugivory for all frugivorous vertebrates at Crater, we generated a crude “index of importance” for each species. Using the fruit size and mass data from 400 plant species, we exclude fruits either too large or too heavy for each frugivore to disperse, yielding a “possible diet” for each species. Four species (a cassowary, a hornbill, a h fruit pigeon and a flying fox) stand out as being crucial dispersers for a large subset of the plant community. The frugivore with the highest importance ranking, Casuarius bennetti, is highly effective as a disperser. Cassowaries appear to be a keystone frugivore, especially for large-fruited plant species (67 species > 50 g at our study site). The method employed is fairly simple and quickly identifies candidates for keystone frugivore status. However, further life history studies are recommended for confirmation of f importance when using this method.

Differential effects of mammalian seed predators on the regeneration of five Papua New Guinean tree species and implications for sapling recruitment

Althoughherbivoresmayaccountforasignificantsourceofseedandseedlingmortalityinmanytropicaltree species, plant species differ in their response to seed damage. Here we investigate the relative effects of seed predation on the regeneration of five tree species in a mid-elevation Papua New Guinean rain forest. Exclosure treatments and shade-house experiments were monitored from November 2004 to March 2006 to assess the differential effects of seed predation on seed viability and seedling growth. Results indicate that although seed predators attack all five focalspecies,theyinfluencetheseedlingpopulationsintwo,CerberafloribundaandMicrocosgrandiflora,andminimally affecttheseedlingpopulationsofTerminaliaimpediens,PandanuspenicillusandEndiandralatifoliaintheyearsmeasured. Predation and germination frequencies were compared to the abundance of focal species at several life stage classes to explore potential correlations between species-specific seed mortality patterns and life stage distributions. We found that the species-specific influence of mammalian seed predators correlated with abundance distributions in three life stages.Specieswithhighsurvivorshipafterseedpredatorattacksdisplayedasignificantdecreaseinabundancefromthe seedling-to-sapling transition, while those species with high seed mortality demonstrated relatively even distributions of seedlings, saplings and adults (>10cm dbh). These contrasting patterns suggest that differential seed predation effects on regeneration may play a key role in the recruitment of individuals to the sapling stage.

Survival rates of 'rattus verecundus' and 'paramelomys platyops' in a murid rich tropical rainforest of Papua New Guinea

Estimations of survival rates of small mammal populations that occur on the island of New Guinea are crucial for conservation and management strategies. Here, we used mark-recapture data in programme MARK to estimate apparent survival and detection of two murid species in a tropical rainforest in Papua New Guinea. The most parsimonious model allowed survival and recapture probability to vary by species. Across the two species, Rattus verecundus generally had lower survival rates, but higher recapture probabilities, whereas Paramelomys platyops had higher survival rates but lower recapture probabilities. Since many small mammal species that occur in New Guinea are already listed under the IUCN red list for Threatened Species, similar studies can be replicated targeting the threatened species to provide information to wildlife managers for management and conservation decision.