Mark J. Butler

Life-History Evolution in Guppies. VII. The Comparative Ecology of High- and Low-Predation Environments

Prior research has demonstrated a strong association between the species of predators that co‐occur with guppies and the evolution of guppy life histories. The evolution of these differences in life histories has been attributed to the higher mortality rates experienced by guppies in high‐predation environments. Here, we evaluate whether there might be indirect effects of predation on the evolution of life‐history patterns and whether there are environmental differences that are correlated with predation. To do so, we quantified features of the physical and chemical environment and the population biology of guppies from seven high‐ and low‐predation localities. We found that high‐predation environments tend to be larger streams with higher light levels and higher primary productivity, which should enhance food availability for guppies. We also found that guppy populations from high‐predation environments have many more small individuals and fewer large individuals than those from low‐predation environments, which is caused by their higher birth rates and death rates. Because of these differences in size distribution, guppies from high‐predation environments have only one‐fourth of the biomass per unit area, which should also enhance food availability for guppies in these localities. Guppies from high‐predation sites allocate more resources to reproduction, grow faster, and attain larger asymptotic sizes, all of which are consistent with higher levels of resource availability. We conclude that guppies from high‐predation environments experience higher levels of resource availability in part because of correlated differences in the environment (light levels, primary productivity) and in part as an indirect consequence of predation (death rates and biomass density). These differences in resource availability can, in turn, augment the effect of predator‐induced mortality as factors that shape the evolution of guppy life‐history patterns. We found no differences in the invertebrate communities from high‐ and low‐predation localities, so we conclude that there do not appear to be multitrophic, indirect effects associated with these differences in predation.

Ecology: Avoidance of disease by social lobsters

Transmissible pathogens are the bane of social animals, so they have evolved behaviours to decrease the probability of infection. There is no record, however, of social animals avoiding diseased individuals of their own species in the wild. Here we show how healthy, normally gregarious Caribbean spiny lobsters (Panulirus argus) avoid conspecifics that are infected with a lethal virus. Early detection and avoidance of infected, though not yet infectious, individuals by healthy lobsters confers a selective advantage and highlights the importance of host behaviour in disease transmission among natural populations.

Sperm economy and limitation in spiny lobsters

Abstract Sperm limitation, when female fertilisation success is constrained by the supply of sperm, is generally perceived to be an uncommon feature of reproduction in species which directly transfer gametes during copulation. Male size, previous copulations, and the balance of expected reproductive return and future mating opportunity may, however, limit the amount of sperm males transfer to females. We used laboratory experiments where mate size could be manipulated and its consequences on spermatophore size and clutch size determined, to show that in two genera of spiny lobsters (Crustacea: Palinuridae) male reproductive output limits the size of clutches brooded by females. In Panulirus argus from the Florida Keys, we show that while male size affects spermatophore area, males also vary the amount of ejaculate positively with female size. Furthermore, the area of the spermatophore has a greater influence than female size on subsequent clutch weight. In Jasus edwardsii from New Zealand, female size, male size and mate order all affect clutch weight. In both species, clutches fertilised by small males in the laboratory are significantly smaller than clutches fertilised by large males. These results suggest that to ensure they receive sufficient sperm, females should either mate several times prior to oviposition, mate as early as possible in the reproductive season, or choose large, preferably unmated males as partners and thus compete with other females for preferred males. Sperm-limited female fecundity has the potential to limit the egg production of fished populations where large males are typically rare.

Thinking and managing outside the box: coalescing connectivity networks to build region-wide resilience in coral reef ecosystems

As the science of connectivity evolves, so too must the management of coral reefs. It is now clear that the spatial scale of disturbances to coral reef ecosystems is larger and the scale of larval connectivity is smaller than previously thought. This poses a challenge to the current focus of coral reef management, which often centers on the establishment of no-take reserves (NTRs) that in practice are often too small, scattered, or have low stakeholder compliance. Fished species are generally larger and more abundant in protected reserves, where their reproductive potential is often greater, yet documented demographic benefits of these reproductive gains outside reserves are modest at best. Small reproductive populations and limited dispersal of larvae play a role, as does the diminished receptivity to settling larvae of degraded habitats that can limit recruitment by more than 50%. For “demographic connectivity” to contribute to the resilience of coral reefs, it must function beyond the box of no-take reserves. Specifically, it must improve nursery habitats on or near reefs and enhance the reproductive output of ecologically important species throughout coral reef ecosystems. Special protection of ecologically important species (e.g., some herbivores in the Caribbean) and size-regulated fisheries that capitalize on the benefits of NTRs and maintain critical ecological functions are examples of measures that coalesce marine reserve effects and improve the resilience of coral reef ecosystems. Important too is the necessity of local involvement in the management process so that social costs and benefits are properly assessed, compliance increased and success stories accrued.

Larval Connectivity and the International Management of Fisheries

Predicting the oceanic dispersal of planktonic larvae that connect scattered marine animal populations is difficult, yet crucial for management of species whose movements transcend international boundaries. Using multi-scale biophysical modeling techniques coupled with empirical estimates of larval behavior and gamete production, we predict and empirically verify spatio-temporal patterns of larval supply and describe the Caribbean-wide pattern of larval connectivity for the Caribbean spiny lobster (Panulirus argus), an iconic coral reef species whose commercial value approaches

Laboratory predation on the Trinidadian guppy: implications for the size-selective predation hypothesis and guppy life history evolution

1 billion USD annually. Our results provide long sought information needed for international cooperation in the management of marine resources by identifying lobster larval connectivity and dispersal pathways throughout the Caribbean. Moreover, we outline how large-scale fishery management could explicitly recognize metapopulation structure by considering larval transport dynamics and pelagic larval sanctuaries.

Transmission of Panulirus argus virus 1 (PaV1) and its effect on the survival of juvenile Caribbean spiny lobster.

Differences in size-specific predation among populations, attributable to different predator guilds, is believed to be the selective agent responsible for the evolution of disparate life history characteristics in Trinidadian guppies (Poecilia reticulata). Yet, the efficacy of this mechanism is inadequately tested. In this study, populations of different-sized guppies were exposed to individuals of two natural predatory species, the pike cichlid Crenicichla alta and the killifish Rivulus harti, under conditions of varying prey (guppy) density and habitat complexity in the laboratory

The Complete Development of Larval Caribbean Spiny Lobster Panulirus argus (Latreille, 1804) in Culture

The Caribbean spiny lobster Panulirus argus, an important fisheries species, is host to Panulirus argus virus 1 (PaV1), a lethal, unclassified virus--the first found in any species of lobster--prevalent in juvenile lobsters. We describe a series of laboratory experiments aimed at assessing the likely modes of disease transmission, determining the survival of lobsters relative to each transmission pathway and identifying potential alternate hosts. Given evidence for lower prevalence of PaV1 in large lobsters, the effect of lobster size on susceptibility was also examined. Results demonstrated that PaV1 can be transmitted to juvenile lobsters via inoculation, ingestion of diseased tissue, contact with diseased lobsters and--among the smallest juveniles--through water over distances of a few meters. Contact and waterborne transmission, the most likely modes of transmission in the wild, were less efficient than inoculation or ingestion. Nevertheless, about half of the smallest lobsters in contact and waterborne trials contracted the disease and died within 3 mo. Other decapods that co-occur with P. argus (e.g. spotted lobster P. guttatus, stone crab Menippe mercenaria, channel crab Mithrax spinosissimus) did not acquire the disease after inoculation with PaV1-infected hemolymph. Our results confirmed that PaV1 is highly infectious and lethal to juvenile P. argus, particularly early benthic juveniles in the wild, and, hence, is a threat to mariculture.

Octopuses influence den selection by juvenile Caribbean spiny lobster

The Caribbean spiny lobster (Panulirus argus) is the most widespread, commercially important, and extensively studied spiny lobster in the western hemisphere, yet until now it has never been successfully reared through all its planktonic (phyllosomal) stages from egg to early benthic juvenile. Here we describe the development of phyllosomal P. argus in culture including the growth, duration, and morphology for 10 distinct stages. Phyllosomata were cultured from egg to juvenile in two ways: 1) in individual cultures using small glass bowls (120 and 400 mL) to determine individual growth, and 2) in group culture using a 40 L elliptical tank to obtain samples for morphological descriptions. Six of the 20 phyllosomata cultured individually (at 25-278C ) metamorphosed after 18-21 molts (mean1⁄420) to the puerulus stage at 140-198 days (mean1⁄4 174 days). Body lengths of the final stage phyllosomata and pueruli ranged from 25.6 to 28.2 mm (mean1⁄4 27.0 mm) and 16.4 to 17.5 mm (mean1⁄4 17.0 mm), respectively. Of the 550 mass cultured (at 258C) phyllosomata, 146 were sampled for morphological examination and subsequently divided into 10 stages, each described and illustrated herein. This is the first of the five Panulirus species known from the Atlantic Ocean to be cultured completely from hatch to settlement. This success is crucial for future research on larval behavior and dispersal and may renew interest in aquaculture of this economically consequential species.

Settlement of Spiny Lobster, Panulirus Argus (Latreille, 1804), in Florida: Pattern Without Predictability?

Octopuses are notorious predators of crustaceans, yet knowledge of their interactions with lobsters is largely anecdotal. Whether by preying on juvenile lobsters or by competing with them for dens or bivalve prey, octopuses should influence the den selection and therefore spatial distribution of lobsters. Lobsters are chemosensitive, so if the interaction is strong, they may respond to chemical cues produced by octopuses and avoid dens or areas where octopuses dwell. In mesocosms, juvenile Caribbean spiny lobsters (Panulirus argus) avoided dens emanating octopus chemical signals. Field manipulations of artificial dens at several spatial scales (<0.1 m to 10 m) showed that the distribution of lobsters was significantly influenced by the proximity of octopuses. Lobsters were significantly less likely to inhabit dens within 2 m of an octopus den, but this strong negative effect disappeared when dens were 10 m apart.