James J. Roper

Phenological patterns among plant life-forms in a subtropical forest in southern Brazil

Phenological patterns in tropical plants usually are associated with the clear seasonality of rainfall associated with very different wet and dry seasons. In southern Brazil, in a subtropical forest with no pronounced dry season (average annual precipitation = 1389 mm, minimum monthly average c. 75 mm), plant phenology was studied to test for patterns (periodicity), to examine how phenological patterns vary among life-forms, and to test whether phenological cycles are associated with climatic variables. Thirty-seven plant species in four life-forms (trees, shrubs, lianas and epiphytes) were studied for 2 yr (1996-98) in an Araucaria forest remnant in southern Brazil, in the state of Paraná. Correlation and multiple regression methods established relationships between phenology and climate in terms of daylength, temperature and rainfall. In this Araucaria forest, plants showed seasonality in most life-forms and phenological phases. Leaf-fall, with its peak during the drier months (April to July), was the most seasonal. Flushing and flowering occurred during the wetter months (September to December), while fruiting occurred all year long. Phenologies varied among life-forms, and were strongly associated with daylength or temperature of preceding months, suggesting that plants receive their phenological cues well in advance of their phenological response. Phenologies in this Araucaria forest appear to be associated with the most predictable and highly correlated of the climatic variables, daylength and temperature and least so with rainfall, which is unpredictable.

Use of artificial substrata by introduced and cryptogenic marine species in Paranaguá Bay, southern Brazil

Abstract Ports are important locations for the introduction of marine species, while marinas and pontoons often serve as secondary habitats for these species. In a marina near Paranaguá Port, a major international port in southern Brazil, the encrusting community was studied to (i) identify possibly introduced species, and (ii) examine the use of artificial substrata by these species. Samples (20 × 20 cm) were taken from fibreglass floats (boardwalks and boat hulls) and concrete columns. A total of 85 species were found of which 50 were classified into three categories: four introduced, 33 cryptogenic and 13 native. The introduced species were the hydrozoan Garveia franciscana (on floats, boats and submerged concrete), the polychaete Polydora cornuta (more abundant on floats and submerged concrete) and the barnacles Amphibalanus reticulatus (equally abundant on the three substrata) and Striatobalanus amaryllis (only on floats and submerged concrete). Organisms were most abundant on floating boardwalks, while species richness and composition were similar to that on boat hulls (32 and 37, respectively), which are an important vector for intraregional transport. All substrata supported at least three of the four introduced, and many of the cryptogenic species. The proportion of introduced to the total number of species was greater than observed in other ports. This demonstrates that the introduction potential is great in Paranaguá Bay, especially considering that this study was restricted to one site and sampled only hard substrata. None of the introduced species has yet been identified as invasive, but all are generalists with respect to substratum, indicating their invasive potential. The ability to colonise stable concrete walls shows that they could also colonise the natural granite rocky substrata in the bay, and the ability to colonise floating surfaces indicate their capability of spreading in the region on the hulls of recreational boats.

An experimental test of colonization ability in the potentially invasive Didemnum perlucidum (Tunicata, Ascidiacea)

Exotic species invasions are one of the greatest threats to marine systems and ascidians have many characteristics that favor transport, colonization and establishment into new regions. Didemnum perlucidum is a widespread species that has been introduced into tropical ports around the world. Here we examine the colonizing ability of D. perlucidum by experimental use of artificial plates in a shellfish culture. The experiment comprised paired plates for colonization (bare and occupied) in 16 monthly replicates. Recruitment and space occupation were compared between bare and occupied plates and an estimation of reproductive effort was based on the number of larvae produced in each of ten colonies collected on the culture structures. D. perlucidum reproduced continuously but greatest reproduction occurred between December 2006 and May 2007. While recruitment was somewhat greater (number of new colonies) on bare plates, this species can colonize already occupied substrates and, surprisingly, colony area was always similar between treatments. Thus, while fewer colonies formed on occupied plates, once formed, colonies grew at rates similar to those on clean plates. Thus, D. perlucidum colonizes substrates very efficiently, especially when unoccupied space is available.

Prenuptial agreements: mating frequency predicts gift-giving in Heliconius species.

Theory predicts that when males provision females with nuptial gifts that include nutrients, the degree of polyandry should be positively correlated with the size or quality of the gift. This is because larger and more nutritious gifts tend to increase female refractory period, reducing the chances the female will remate soon. This decreases the likelihood of sperm competiton and consequently increases the donor male fitness. Butterflies in the genus Heliconius Kluk (Lepidoptera: Nymphalidae: Heliconini) exhibit variable mating systems that include monandry and polyandry. In addition to protein in the spermatophore, males increase gift quality by providing females with cyanide, which may contribute to protection of the female or her eggs. We tested whether degree of polyandry and gift quality (spermatophore weight and cyanide content) were correlated in nine Heliconius species from greenhouse populations. As predicted, both spermatophore weight and cyanide content were correlated with mating frequency. This is the first report to show that degree of polyandry correlates with allocation of defensive chemical as part of a nuptial gift.

The role of Asterina stellifera (Echinodermata: Asteroidea) as a predator in a rocky intertidal community in southern Brazil

Populations of Asterina stellifera Mobius, 1859 are declining in southern Brazil and today the species is on the Brazilian list of endangered species. Here we experimentally investigate the ecological role played by A. stellifera as a predator on the rocky substrate community by increasing densities of this species. Starfish taken from other, nearby, locations were added to three replicate plots and their density was maintained every 15 days. None of the total of 32 species that were identified in the encrusting community appeared to be influenced by the experiment. Two species, the barnacle Chthamalus bisinuatus Pilsbry, 1916 and the algae Gracilaria verrucosa (Hudson), showed small apparent responses to predation. We found that A. stellifera only exerts weak predation pressure on the community, even at high densities. This result is strikingly different from that observed for similar species in the northern hemisphere and in Australia.

Edge effects without habitat fragmentation? Small mammals and a railway in the Atlantic Forest of southern Brazil

Edge effects have been studied extensively in fragmented landscapes, often with conflicting findings. Edge effects may also be important in other situations, such as linear clearings (e.g. along roads, power lines or train tracks). We tested for responses of small mammals to a narrow (c.  m) linear clearing created by a railway in the largest area of Atlantic Forest in southern Brazil. Only two environmental variables, light intensity and train noise, were greatest at the edge and decreased with distance from the edge. Temperature differed (greater extremes and more variable) only at the edge itself. The few small mammal species that were only rarely captured at the edge resulted in an apparent edge-effect with respect to species richness. The abundance of small mammals, however, was independent of distance from the railway. There was no correlation between resource availability at the tracks and abundance of small mammals. Edge effects were minimal, which suggests that narrow railways (in contrast with roads) in unfragmented landscapes probably do not have a significant impact (if any) on wildlife, as found elsewhere and especially in tropical forests. The use of railways instead of roads is a potential strategy to minimize the effects of traversing important habitats for commercial reasons.

Population dynamics of the black-cheeked gnateater (Conopophaga melanops, Conopophagidae) in southern Brazil.

Population structure and dynamics of the black-cheeked gnateater (Conopophaga melanops) were studied at Salto Morato Nature Reserve, in Paran´ a, southern Brazil, from October 2006 to September 2007. Territory size and population density, breeding season (timing and length), reproductive success and annual survival rates were estimatedfromsightingsof18markedadultbirdsandthesuccessof18nestingattempts.Theblack-cheekedgnateater is socially monogamous and territorial, with a breeding-season length of approximately 3 mo beginning in early October. Predation caused most nest failures, nest survival was 0.96 d −1 and apparent annual nesting success was 22%, resulting in annual productivity of 0.36 individuals per adult. Apparent adult annual survival was ∼0.44 y −1 . Seventy-five per cent of fledglings survived at least 2 mo after fledging. Two methods of estimating population growth ratesuggestverydifferentrates:r =− 0.04(∼stable),or λvariesbetween0.475-0.616(declining).Yet,lowapparent adult survival suggests that territories are not permanent, perhaps abandoned after nest failure. We find that by estimating population growth, even in short-term studies, testable hypotheses can be generated that will allow better understanding of population dynamics.

Sexual and asexual reproduction in Didemnum rodriguesi (Ascidiacea, Didemnidae)

Sexual and asexual reproduction and associated population dynamics were investigated in the colonial ascidian Didemnum rodriguesi Rocha & Monniot, 1993 (Didemnidae) in southern Brazil. Investment in sexual (production of new individuals) and asexual (colony growth) reproduction was compared between seasons. Permanently marked quadrats were repeatedly photographed to measure changes in colonies. Eggs and larvae were counted monthly in collected colonies. This species alternates seasonally between sexual (summer) and asexual (winter) reproduction. In summer, colonies were smaller, brooded eggs and larvae and recruitment rates were greater, while in winter, colony size was larger and eggs and larvae were absent. There is a relationship between fecundity and colony area. Fragmentation and fusion of colonies were similar in summer and winter, as well as mortality. In conclusion, D. rodriguesi has a lifecycle usual for high latitude ascidians with a limited time length for sexual reproduction and alternate investment in sexual and asexual reproduction along the year.

The Rufous Hornero (Furnarius rufus) nest as an incubation chamber.

Foraging and incubation are mutually exclusive activities for parent birds. A trade-off is generated when a combination of food availability and temperature regulation force birds to choose one and neglect the other, at least temporarily. The Rufous Hornero builds large, oven-like, mud nests, the evolutionary cause of which remains unknown. We tested that temperature variation inside the nest is that which is expected if one function of the nest were for temperate regulation. If so, this would suggest that the nest works as an incubation chamber (but which now may serve more than one function). We divided nests into two natural treatments: nests that received more continuous direct sunshine (sun), and those that received less direct sunshine, due to shade from trees or buildings (shade). Thermometer data loggers were placed in the nest cavity and outside, in the shade of the nest, and temperature was measured every 10min. We predicted that temperatures would consistently be higher and less variable in nests than outside nests. Also, at higher ambient temperatures the nest would function better as an incubation chamber as a consequence of having evolved in a hotter climate. Thus, in Curitiba, where temperatures are lower than where the species (and nest) evolved, nests in greater sunshine should have thermal characteristics that support the incubation chamber hypothesis. Predictions were supported: with Repeated Measures ANOVA and t-tests, we found that temperatures were more constant and higher in nests, especially when in the sun, and as the season progressed (hotter ambient temperatures). We conclude that the large mud nest of the Rufous Hornero works as an incubation chamber that likely evolved to help resolve the incubation-foraging trade-off in the very seasonal and hot regions where the bird evolved. Thus, as an incubation chamber, the nest allows the bird to forage rather than incubate thereby resolving the foraging-incubation trade-off and potentially favoring survival of the adults and their foraging for, rather than incubating, their young. Counter intuitively, in the study area, where the Rufous Hornero is a recent arrival following deforestation, and where the climate is very different from where it evolved, there seems to be no clear thermal benefits for the birds from their energetically expensive mud nest.

Small mammal community structure and vertical space use preferences in nonfragmented Atlantic Forest

Abstract Here we describe a small mammal community in nonfragmented Atlantic Forest in southern Brazil. A total of 146 individuals were live captured on the ground and in trees (total effort: 5600 trap-nights). Twelve species were identified by morphology, and identification of seven species was confirmed by DNA barcoding. Most species were terrestrial, with Euryoryzomys russatus being the most frequently captured, while the rodent Juliomys pictipes was semiarboreal and the marsupial Marmosa paraguayana was arboreal. With the capture of Trinomys iheringi, we extend the species distribution to the south. Species favored in disturbed environments as Oligoryzomys spp. and Akodon spp. were uncommon, and this small mammal community is typical of a well-conserved forest.