The predation gauntlet: early post-settlement mortality in reef fishes

Most marine fishes have pelagic larvae that settle to benthic juvenile/adult habitats. Ecologists have argued that mortality rates are particularly high during the settlement transition, but relevant data have been sparse. Recently, researchers have used several novel techniques to estimate the magnitude of predation mortality during the settlement transition. We used meta-analysis to determine that for 24 taxonomically diverse species in geographically widespread locations, an estimated 55.7% (CI: 43.0–65.5%) of juveniles were consumed within 1–2 days of settlement. Such high mortality highlights this brief period as a key phase in the life history of fishes and supports the view that these communities are strongly influenced by predation. Additionally, we argue that because predators have such strong effects on juvenile survival, the population and community dynamics of reef fishes may be linked to human exploitation of reef predators.     

The role of variance in capped-rate stochastic growth models with external mortality

Techniques from queueing theory can be used to model the growth of individuals in a stochastic environment where the growth rate cannot exceed some physiological maximum. In the simplifying case where there are no metabolic costs and the individual has an unlimited gut size, a general theory for the probability of reaching a target weight is presented. The role of environmental variance is examined in two different cases; randomly varying prey size and clustering in the prey arrival rate. It is argued that when food is scarce environmental stochasticity is beneficial to the individual but when food is abundant it can lower the chance of survival. The growth and recruitment of larval fish is used as an example.     

Settlement and recruitment of three damselfish species: larval delivery and competition for shelter space

Spatial patterns of settlement and abundance of older life stages were examined for three species of damselfish in the genus Dascyllus by monitoring natural colonization of standard amounts of initially empty juvenile microhabitat (anemones for D. trimaculatus; branching coral for D. flavicaudus and D. aruanus) transplanted to a series of sites within lagoons of Moorea, French Polynesia. Large spatial differences in larval colonization were observed, which were temporally consistent but different among the species. At the whole-island scale, D. trimaculatus settled primarily on the northern shore, while settlement of the other two species was greatest at the southern end. The three species also showed different patterns of settlement within lagoons: D. aruanus settled mainly nearer to shore, D. flavicaudus primarily on offshore lagoon portions and D. trimaculatus colonized equally across the lagoons. Among sites around the island, the relative abundance of older juveniles after 10 months was a curvilinear function of the relative abundance of settlers for two species (D. trimaculatus and D. flavicaudus). There was no relationship between patterns of settlement and abundance of older juveniles for D. aruanus, although juvenile abundance was inversely related to that of juvenile D. flavicaudus. At the within-lagoon scale, settlement mirrored almost exactly the relative abundance of older lifestages of D. trimaculatus and D. flavicaudus, whereas there was just a qualitative match for D. aruanus. A competition experiment revealed that juvenile D. flavicaudus had a greater effect on population growth of D. aruanus than vice versa, and this mechanism helped explain why the modification of settlement patterns was greatest in D. aruanus. Interspecific variation in abundance of older stages was shaped to differing extents by both patterns of larval delivery and subsequent density-dependent processes involving competition for shelter space. Received: 9 April 1998 / Accepted: 6 August 1998     

Evidence of density-independent mortality in a settling coral reef damselfish, Chromis viridis

To know if the variation in the number of settling fish larvae can be dampened by density-dependent postsettlement mortality, we investigated the relationship between settler density and predator-induced mortality of a coral reef damselfish, Chromis viridis. Totals of 2, 3, 5, 8, 10, 12, 14, 16, 18, and 20 fish of 10 or 20 mm total length were released in experimental cages enclosing a coral head of Porites rus (to provide settlement habitat) and five predators. The results showed that the mortality rate of both 10- and 20-mm fish was density independent.     

Small-scale demographic variability of the biocolor damselfish, <Emphasis Type="Italic">Stegastes partitus</Emphasis>, in the Florida Keys USA

The demographic responses of reef fish to their environment can be complex and in many cases, quite strong. Growth, mortality, longevity, and even reproductive effort have been demonstrated to vary for the same species of reef fish over scales of 100s to 1,000s of kilometers due to physiological and ecological interactions. Though few studies have explicitly documented it, this sort of habitat-mediated demography can also exist at very local scales. Here we present the results of a 2-year study of the bicolor damselfish, Stegastes partitus, in the Florida Keys, USA. We measured density and distribution, calculated key demographic rates (growth, survival, and fecundity), and characterized the environment (resident fish assemblage, substrate type and complexity, and food availability) of populations living in two adjacent but different habitats, the continuous fore reef and patchy back reef. Fish on the fore reef had an elevated growth rate and asymptotic size, increased mortality, and higher fecundity than fish on the back reef. We identified four potential causative mechanisms for these differences: food availability; competition; intraspecific density-dependent effects; and predation risk. Our data did not support an effect of either food availability or intraspecific density-dependence, but rather suggested that demographic responses are affected by both competition and predation risk.     

Recruiting juvenile damselfish: the process of recruiting into adult colonies in the damselfish Stegastes nigricans

Juveniles of Stegastes nigricans occur in adult colonies, solitarily, and occasionally in juvenile colonies. We concentrated on solitary juveniles and those in adult colonies. We examined the costs and benefits of different settlement strategies, quantified the territory requirements of adults, and investigated the process of how juveniles make the transition to adult territorial fish. An adequate adult territory lies next to those of other adults, is proportional in area to the size of the adult, and contains a refuge tunnel whose entrance is sufficiently large. Compared with solitary juveniles, those <4 cm total length inhabiting adult colonies experienced reduced heterospecific competition for algal food and consequently benefited from a greater density of algae. A cost of recruiting into an adult colony, however, was increased attacks by adults. Juveniles that settled in adult colonies avoided attacks by retreating into small holes inaccessible to adults. As juveniles in adult colonies grew, they were chased less often by adults, whereas they themselves chased adults and heterospecific fish more often. Because territory size correlated with fish size in adult colonies, its area had to expand as the young fish grew, and that expansion was done at the expense of neighbors. Obtaining the space needed by an adult may be possible only when the juvenile settles directly into an adult colony. Juveniles that first settle down solitarily, or in juvenile colonies, may later attempt to enter adult colonies. However, because they do so as larger juveniles, they would have difficulty insinuating themselves into small refuges, which is essential for retreat from the adults. Received in revised form: 4 January 2001 Electronic Publication     

Fine-scale temporal variation in recruitment of a temperate demersal fish: the importance of settlement versus post-settlement loss

In order to understand variability in recruitment to populations of benthic and demersal marine species, it is critical to distinguish between the contributions due to variations in larval settlement versus those caused by post-settlement mortality. In this study, fine-scale (1–2 days) temporal changes in recruit abundance were followed through an entire settlement season in a temperate demersal fish in order to determine 1) how dynamic the process of recruitment is on a daily scale, 2) whether settlement and post-settlement mortality are influenced by habitat structure and conspecific density, and 3) how the relationship between settlement and recruitment changes over time. Settlement is considered to be the arrival of new individuals from the pelagic habitat, and recruitment is defined as the number of individuals surviving arbitrary periods of time after settlement. Replicate standardized habitat units were placed in 2 spatial configurations (clumped and randomly dispersed) and monitored visually for cunner (Tautogolabrus adspersus) settlement and recruitment every 1–2 days throughout the settlement season. The process of recruitment in T. adspersus was highly variable at a fine temporal scale. Changes in the numbers of recruits present on habitat units were due to both settlement of new individuals and mortality of animals previously recruited. The relative importance of these two processes appeared to change from day to day. The magnitude of the change in recruit number did not differ between the clumped and random habitats. However, post-settlement loss was significantly greater on randomly dispersed than clumped habitats. During several sampling dates, the extent of the change in recruit abundance was correlated with the density of resident conspecifics; however, on other dates no such relationship appeared to exist. Despite the presence of significant relationships between the change in recruit number and density, there was no evidence of either density-dependent mortality or settlement. Initially, there was a strong relationship between settlement and recruitment; however, this relationship weakened over time. Within 2 months after the cessation of settlement, post-settlement loss was greater than 99%, and no correlation remained between recruitment and the initial pattern of settlement. The results of this study demonstrate that the spatial arrangement of the habitat affects the rate and intensity of post-settlement loss. Counter to much current thinking, this study suggests that in order to understand the population ecology of reef fishes, knowledge of what habitats new recruits use and how mortality varies with structural aspects of the habitats is essential.     

Early life-history dynamics of Caribbean coral species on artificial substratum: the importance of competition, growth and variation in life-history strategy

The development of a coral community was monitored for 6 years (1998–2004) on 46 m² of artificial settlement substrate in Curaçao, Netherlands Antilles. Growth and survival of recruits (n=1385) belonging to 16 different species were quantified in relation to characteristics of the benthic community developing around them. The early life history dynamics (i.e. growth rate, growth strategy and survival) of corals differed among species although these differences were small for species occupying similar habitats (i.e. underside versus topside of substratum). In contrast to recruit survival, juvenile growth rates were highly variable and unrelated to benthic community structure, at least at the scale of this study. Competing benthic organisms affected coral recruitment success through space preemption (mainly by macroalgae) or recruit overgrowth (mainly by sponges). The results highlight the small spatial scale (mm–cm) at which the processes responsible for recruitment success or failure occur and emphasize the need to include such small-scale observations in studies of coral early life-phase dynamics.     

Molecular species identification of morphologically similar mussel larvae reveals unexpected discrepancy between relative abundance of adults and settlers

Understanding the relative importance of larval supply vs. post-settlement mortality underlies studies of marine invertebrate recruitment, yet is often hampered by researchers' inability to identify species among morphologically similar larvae or early juveniles. In New Zealand, two species of co-occurring intertidal mytilid mussels have morphologically indistinguishable settlers: the blue mussel Mytilus galloprovincialis, which is often numerically dominant in the mid-zone of the rocky intertidal, and the ribbed mussel Aulacomya atra maoriana which is often much less abundant. In this study, we obtained samples of newly settled mussels from 6 sample dates April-May 2005 from the rocky intertidal in Wellington Harbour, New Zealand. We used PCR-RFLP of the cytochrome c oxidase subunit I (COI) mitochondrial gene region to identify settlers to species. Of a total of 224 settlers that could be identified, 64% were identified as Mytilus galloprovincialis and 36% as Aulocomya atra maoriana. The percentage of A. atra maoriana in the samples was unexpectedly high and ranged from 22–50% among the sample dates. This study reinforces the need to quantify larval supply at the species level to understand the relative importance of pre- and post-settlement mortality, and also demonstrates the usefulness of the COI region as a species-specific marker for identifying mussel larvae and juveniles.     

Roles of larval supply and behavior in determining settlement of barnacles in a temperate mangrove forest

Recruitment is often a major influence on the spatial distribution of populations of benthic marine invertebrates, but the contributions of different components of recruitment are not well known, with the added complication that the relative importance of various life-history processes may be scale-dependent. Previously, we have shown that over a large scale across a mangrove (Avicennia marina) forest in southeastern Australia, settlement of the barnacle Elminius covertus explained its patterns of recruitment, which in turn explained the distribution of adults on mangrove pneumatophores. Post-settlement mortality had little influence on this pattern. In contrast, small-scale vertical distributions of adult barnacles along individual pneumatophores were determined by the pattern of recruitment, which differed from the pattern of settlement, so post-settlement mortality determined the vertical patterns of adults.

In this study, we tested whether larval supply and/or settlement behavior influence the observed settlement patterns of E. covertus across a forest (from seaward to landward zones). We also tested whether larval supply could explain the vertical settlement patterns along the pneumatophores. A pumping system was used to collect cypris larvae from seaward, mid and landward zones of a mangrove forest and an adjacent, unvegetated shore and from three heights above the sediment surface. We also used transplantation of wooden stakes bearing microbial films and barnacle recruits between horizontal zones of the forest to determine whether settlement was influenced by these films or recruits.

Both cyprid supply and cyprid behavior were important factors in determining the patterns of settlement of E. covertus across the forest. Cyprid supply was a result of three-fold differences in immersion times of different (landward, mid and seaward) zones across the forest and a decrease in density of cyprids in the water column from the seaward zone of the forest to the landward sections. In the absence of mangroves immediately adjacent to the forest, there was no temporally consistent difference in cyprid density across the shore and even the differences in immersion time did not produce consistent differences in cyprid supply across the shore. Wooden substrata that had been immersed at seaward sections of the forest attracted consistently more settlers than substrata immersed initially at other sections of the forest and settlement could be induced beyond the normal distribution of adults of E. covertus by stakes transplanted from the seaward zone.

The vertical settlement pattern could not be explained by the supply of cyprids, suggesting that larval behavior must determine the vertical settlement pattern.     

Ultraviolet absorbance of the mucus of a tropical damselfish: effects of ontogeny, captivity and disease

The ultraviolet (UV) absorbance of the mucus of a Great Barrier Reef damselfish Pomacentrus amboinensis was investigated with regard to ontogeny and time spent in captivity. The UV absorbance of P. amboinensis mucus increased with fish size and decreased with time spent in captivity. The wavelength of maximum absorbance of the mucus did not change with fish size, but shifted towards shorter wavelengths with increasing time spent in captivity. The UV absorbance of the mucus of fish with 'fin rot' was compared to that of similar healthy individuals, and a significant decrease in UV absorbance of unhealthy fish mucus was detected; no wavelength shifting occurred. Pomacentrus amboinensis appears to sequester mycosporine-like amino acids from the diet in order to protect epithelial tissues from UV damage, and decreases in UV absorbance in captive fish were probably due to insufficient dietary availability.     

Pharmacological Induction of Larval Settlement and Metamorphosis in the Blue Mussel Mytilus edulis L.

The blue mussel Mytilus edulis L. is an important aquaculture and fouling species in northern seas. Although the general role of chemical cues for settlement of larvae of the blue mussel has been proposed, few studies have focused on induction of settlement and metamorphosis by pharmacological agents. In this study, the induction of larval settlement of the blue mussel by pharmacological compounds was investigated through a series of laboratory experiments with an aim of identifying artificial cues for laboratory bioassay systems in fouling and antifouling research. Gamma-aminobutiric acid (GABA), dihydroxyphenyl L-alanine (DOPA), isobutyl methylxanthine (IBMX) and acetylcholine chloride (ACH) at 10^{m 7}-10^{m 2} M as well as KCl at 10-40 mM K⁺ in excess of the level in normal seawater were tested for their inductive effect on larval settlement. In filtered seawater (FSW) <9% of the larvae settled after 48 h. Elevated K⁺ and GABA levels had no effect on larval settlement and metamorphosis. DOPA at 10^{m 5} M and IBMX at 10^{m 6}-10^{m 4} M induced 41-83% larval settlement and ACH at 10^{m 7}-10^{m 5} M induced < 40% larval settlement. While the highest settlement rates were observed after 48 h exposure to the chemicals, most of the larvae settled within 24 h. Compounds at concentrations of 10^{m 3}-10^{m 2} M were either toxic to larvae or retarded the growth of the post-larvae shell. Juveniles resulting from induction by lower concentrations of chemicals had a very high survival rate, completed metamorphosis and grew as well as the juveniles that metamorphosed spontaneously. IBMX at 10^{m 6}-10^{m 4} M and L-DOPA at 10^{m 5} M are effective agents for induction of settlement and metamorphosis for future studies using juvenile M. edulis.     

Aggression in damselfish: habituation by adults of Pomacentous parritus to juvenile intruders

Synopsis Successful recruitment of juvenile coral reef fishes may depend, in part, upon the aggressive behavior of adults already on the reef. In addition to initial levels of aggression, changes in aggressive behavior of adults, e.g., due to habituation, may have an even greater influence on recruiting juveniles. Adult males of the bicolor damselfish, Pomacentrus partitus, were used as subjects to study habituation of aggression toward conspecific and congeneric (P. variabilis) juveniles. Adults, held in a 1000 liter aquarium, habituated after 4 hours of constant exposure to juveniles restrained in a 1 liter model bottle. Stimulus strength of the juveniles depended on their species identity, size and proximity to the resident adult's shelter. There was a recovery of aggression with a change in stimulus location, but at the same location, a stimulus of greater strength was required to bring about recovery. The implications of these findings for coral reef fish community structure are discussed.     

Larval growth dynamics ofHemipyrellia ligurriens (Calliphoridae) andBoettcherisca formosensis (Sarcophagidae) in crowded and uncrowded cultures

Larval growth patterns of Hemipyrellia ligurriens (Calliphoridae) and Boettcherisca formosensis (Sacophagidae) in crowded and uncrowded cultures were compared. Growth of the larvae followed a sigmoid curve. The highest larval growth rates were 0.33 and 0.36 mg h⁻¹ for uncrowded and crowded H. ligurriens respectively. The corresponding figures were 2.38 and 1.23 mg h⁻¹ for B. formosensis. Larvae of both species attained maximum weight earlier in crowded cultures than in uncrowded cultures, although the final weights attained in crowded cultures were less. The earlier period of most rapid growth in both species was interpreted as a result of intraspecific facilitation at higher larval densities. Uncrowded B. formosensis had a shorter larval to pupal development and an earlier period of most rapid growth than uncrowded H. ligurriens, suggesting the former may be superior in exploiting carcasses with limiting food.     

Will providing a filamentous substratum in the water column and shell litter on the bottom increase settlement and post-larval survival of the scallop Argopecten purpuratus?

The marked variability in the natural recruitment of Argopecten purpuratus, a common characteristic for many marine invertebrates with a pelagic larval stages, with important consequences for community functioning, is a problem for the fishery on this species. We ran experiments in the subtidal zone in Tongoy Bay, Chile, to test whether providing a filamentous settlement substratum in the water column and shell litter on the bottom would increase the settlement and post-larval survival of scallops. We placed collectors made of Netlon® 50 cm above the sand and mud bottoms, and three and a half months later there were significantly more scallop spat on the bottom under the collectors (38.5 ind m^− 2), than in areas without collectors (0 ind m^− 2), or in controls where collectors were installed but a bag around the collector prevented the juveniles from falling to the bottom (4.8 ind m^− 2). Also, the addition of either entire or broken scallop shells to the bottom resulted in increased settlement of juveniles on the bottom (33.7 ind m^− 2 with entire shells and 48.1 ind m^− 2 with broken shells), compared to plots where no shell debris was added (0 ind m^− 2). The 2 week survival rate of juveniles (< 3 mm shell height) added to plots covered with entire scallop shells (12.4%) and to plots covered with broken shells (15.1%) was greater than in plots where we did not add shells (3.5%). These results suggest that substrate availability explains spatial variability of recruitment for this species, while temporal variability (between years) is mainly the consequence of larval supply. The manipulation of substrates can locally increase settlement, but will not remove the temporal variability. Whereas our experiments provide useful insights into strategies for managing or establishing local scallop populations, experiments over a longer term and at a large scale are needed to further understand the community functioning in order to develop a strategy for managing this fishery resource.     

Ontogeny of feeding in two native and one alien fish species from the Murray-Darling Basin, Australia

Investigations into the feeding of the early stages of fishes can provide insights into processes influencing recruitment. In this study, we examined ontogenetic changes in morphology and feeding behaviour of two native Australian freshwater species, Murray cod, Maccullochella peelii peelii, and golden perch, Macquaria ambigua, and the alien species, common carp, Cyprinus carpio. Murray cod free embryos are large and well developed at the onset of feeding, whereas the other two species begin exogenous feeding much younger and are smaller and less-developed. Carp commence exogenous feeding 3 days earlier than golden perch, and show more advanced development of the eyes and ingestive apparatus. We conducted feeding experiments, presenting larvae of the three species with a standardised prey mix (comprising equal numbers of small calanoid copepods, large calanoid copepods, small Daphnia, and large Daphnia). Larvae of most tested ages and species showed a preference for mid-sized prey (300–500 μm wide). This was true even when their gapes substantially exceeded the largest prey offered. Daphnia were consumed more than similar-sized copepods. The results of this study suggest that survival through their larval period will be threatened in all three species if catchable prey <500 μm in width are not available throughout such time. They also suggest that interspecific competition for prey may occur, especially when larvae are very young. The precocious development of structures involved in feeding and the extended transition from endogenous to exogenous feeding of early carp larvae are likely to have contributed to the success of this species since its introduction to Australia.     

A key phase in the recruitment dynamics of coral reef fishes: post-settlement transition

Synopsis Recent studies of recruitment dynamics in demersal fishes have placed major emphasis on presettlement mortality, and little on events bridging late larval and early juvenile periods. Observations on 68 taxa of Caribbean coral reef fishes before and during settlement revealed the existence of a distinct post-settlement life phase called the transition juvenile, associated with the act of recruitment. Transition juveniles were found as solitary individuals, in conspecific groups, or in heterospecific groups. The groups were either uniform or heterogenous in appearance. The complexity of the transition phase and its apparently widespread occurrence in coral reef fishes suggests that important aspects of population structure may be determined between settlement and first appearance as a full-fledged juvenile.     

Processes regulating early post-settlement habitat use in a subtidal assemblage of brachyuran decapods

In highly mobile animals post-settlement dispersion of juveniles can strongly influence the observed patterns of abundance and distribution. To explore the relative importance of factors regulating the use of habitat by crabs we performed a multi-species manipulative experiment in a subtidal environment of the central Chilean coast. First, demographic patterns were established by performing a year-round crab survey in three discrete and well-known subtidal crab habitats: (1) algal turf, (2) cobbles and (3) shell hash. Second, habitat preferences were experimentally evaluated using concrete trays that were filled with different substrate types that simulate natural habitats. Settlement and recruitment rates were estimated from experimental trays that were left in the field and surveyed after 2 weeks (complete experiment was repeated 7 times throughout 1 year). Third, mortality, due to predation, was assessed by covering 50% of the trays with a 4-mm mesh-size screen that excluded large predators (i.e., fishes, shrimps). Fourth, habitat colonization rates were evaluated by quantifying the arrival, into open trays, of large juveniles (secondary dispersal). The most abundant species in this system (Paraxhantus barbiger, Cancer setosus, Taliepus dentatus and Pilumnoides perlatus) displayed clear habitat preferences at the time of settlement, evidenced by differences in density of recruits among habitats. Recruitment regulation by predation seemed to explain the observed patterns in only one case. For most species, however, evidence of ontogenetic change in the use of habitat, through active habitat redistribution by large juveniles, was detected. Thus, secondary dispersal among habitats seems to outweigh the influence of megalopae's habitat selection and post-settlement mortality as responsible for the observed demographic patterns.     

Larval development and foraging behavior of Erythrodiplax abjecta (Rambur) (Anisoptera: Libellulidae) in captivity

Understanding the life cycle of Neotropical odonate species is essential given our scant knowledge of this region. In this paper, we examine growth ratio between instars, development patterns, and active/passive feeding behavior of the Andean dragonfly Erythrodiplax abjecta (Rambur, 1842). Larvae were obtained from eggs laid by two females in the laboratory and were maintained at 12–34 °C in individual containers until either their emergence or their death. Larvae hatched 26–57 days after laying, and the total development time was determined as being 316 (SD ± 6.6) days, including 13 instars. Larval instars were characterized using six morphometric variables. The foraging behavior was analyzed considering the time of day and the percentage of the background covered by detritus. The growth ratios between successive instars averaged 1.9 for FW pad length, 1.6 for HW pad length and 1.2 for head width, head length, metathoracic leg length, and total length. Neither the active foraging nor the sit-and-wait foraging behavior were affected by either time of the day or the percentage of background covered by detritus. Erythrodiplax abjecta is univoltine and has a slow lifestyle associated with lentic perennial waters, where larval development and growth rates are low. We provide an equation to estimate the E. abjecta larval instars from field specimens.Given that our results were obtained from the eggs laid by only two females, further studies including a larger sample size are needed to validate their generality.     

Growth and survival of two north Australian relictual tree species, <Emphasis Type="Italic">Allosyncarpia ternata</Emphasis> (Myrtaceae) and <Emphasis Type="Italic">Callitris intratropica</Emphasis> (Cupressaceae)

Allosyncarpia ternata (an angiosperm) and Callitris intratropica (a gymnosperm) are two fire-sensitive tree species of the Australian monsoonal tropics. Studies using historical aerial photography have revealed recent expansion of A. ternata rainforests. There has simultaneously been a widespread collapse of C. intratropica populations in northern Australian savannas, presumably because of cessation of traditional Aboriginal landscape burning. To explain the demography behind these contrasting trends, stand structure, survival, and growth of the two species were recorded over a 16-year period at the boundary of a rainforest patch and also in adjacent savanna, in Kakadu National Park. Ages of the largest trees of each species, estimated by using a Bayesian analysis of tree-diameter increments, were approximately 433 years for A. ternata and 235 years for C. intratropica on the rainforest boundary, and 417 years for C. intratropica in the adjacent savanna. Densities of juveniles (seedlings and re-sprouts <0.5 m high) were 325–6,000 times higher for A. ternata than for C. intratropica. Life-table calculations indicated there was sufficient recruitment of A. ternata, but not C. intratropica, to overcome observed mortality rates and maintain a stable population. This is almost certainly because A. ternata re-sprouts prolifically after fire whereas C. intratropica is an obligate seeder. These results highlight the critical need for careful fire management to maintain populations of a characteristic Australian gymnosperm over much of its range.