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PubMed2004

Pollination and reproductive biology of twelve species of neotropical Malpighiaceae: stigma morphology and its implications for the breeding system.

BACKGROUND AND AIMS: This study on reproductive biology examines the stigmatic morphology of 12 Brazilian Malpighiaceae species with regard to their pollination and breeding system. METHODS: The species were studied in natural populations of a semi-deciduous forest fragment. Style tips were processed for observation by SEM and pollen-tube growth was analyzed under fluorescence microscopy. The breeding system was investigated by isolating flowers within waterproof bags. Floral visitors were recorded through notes and photographs. KEY RESULTS: Flowers are yellow, pink or white, protogynous, herkogamous and sometimes lack oil glands. While Banisteriopsis pubipetala has functional female flowers (with indehiscent anthers), 11 species present hermaphrodite flowers. Stigmas of these species may be terminal, with a slightly concave surface, or internal, consisting of a circular cavity with a large orifice, and are covered with a thin, impermeable cuticle that prevents pollen from adhering, hydrating, or germinating. Malpighiaceae have a special type of 'wet' stigma, where a secretion accumulates under the cuticle and is released by mechanical means-mainly rupture by pollinators. Even though six species show a certain degree of self-compatibility, four of them present a form of late-acting self-incompatibility, and the individual of B. pubipetala is agamospermous. Species of Centris, Epicharis and Monoeca bees pollinate these flowers, mainly collecting oil. Some Epicharis and Monoeca species collected pollen by vibration. Paratetrapedia and Tetrapedia bees are pollen and oil thieves. CONCLUSIONS: The Malpiguiaceae species studied are pollinator-dependent, as spontaneous self-pollination is limited by herkogamy, protogyny and the stigmatic cuticle. Both the oil- and pollen-collecting behaviours of the pollinators favour the rupture of the stigmatic cuticle and the deposition of pollen on or inside the stigmas. As fruit-set rates in natural conditions are low, population fragmentation may have limited the sexual reproduction of these species.

Animals↗
PubMed1992

Autogeny in the neotropical sand fly Lutzomyia lichyi (Diptera: Psychodidae) from Colombia.

Host-seeking females of the anthropophilic sand fly, Lutzomyia lichyi (Floch & Abonnenc), collected in Valle, Colombia, were invariably parous. All progeny of these insects reared in the laboratory were autogenous for the first ovarian cycle, producing fertile eggs without a blood meal. The importance of autogeny in Leishmania transmission is discussed briefly.

Animals↗
PubMed1993

Life cycle of Leishmania major (Kinetoplastida: Trypanosomatidae) in the neotropical sand fly Lutzomyia longipalpis (Diptera: Psychodidae).

The development of Leishmania major Yakimoff & Schokhor in the New World sand fly Lutzomyia longipalpis (Lutz & Neiva) was examined by light and electron microscopy. In this unnatural host, parasites differentiated into 10 typical morphological forms, multiplied at three sites, migrated anteriorly and established in the foregut, and attached to gut surfaces. In the blood meal, amastigotes divided and transformed into two successive dividing, stumpy promastigote stages. Elongate nectomonad promastigotes developed from stumpy forms and subsequently rounded up in some flies into paramastigotes and opisthomastigotes. Differentiation into round opisthomastigotes and the apparent fusion of paramastigotes in the blood meal were novel observations in this study. Three nectomonad promastigotes--elongate, short, and metacyclic--were free-swimming in the midgut lumen. Elongate nectomonad promastigotes were highly oriented in the midgut, with their flagella embedded between the epithelial microvilli. Short haptomonad promastigotes were the predominant form attached to the intima of the stomodeal valve, whereas pear-shaped haptomonad promastigotes and paramastigotes colonized surfaces of the esophagus and pharynx. Peripylarian attachment of promastigotes and paramastigotes in the pylorus, ileum, and colon was noted in 21% of flies, suggesting that suprapylarian leishmanias have not lost the ability to colonize the hindgut. L. longipalpis was a successful biological host for L. major, allowing complete development of the parasite.

Animals↗
PubMed2005

Intragenomic heterogeneity of internal transcribed spacer rDNA in neotropical malaria vector Anopheles aquasalis (Diptera: Culicidae).

Intragenomic heterogeneity of the internal transcribed spacer (ITS) array was investigated in Anopheles aquasalis Curry mosquitoes from two geographic locations in each of Brazil and Venezuela, and one in Suriname. Polymerase chain reaction-amplified copies of the ITS were cloned and sequenced. The length of the entire array ranged from 782 to 990 bp, with most variation due to microsatellite insertions in ITS1. We detected 40 different ITSL sequences and 15 different ITS2 sequences of the 71 to 72 clones examined. The sequence divergence within localities ranged from 0.002 to 0.043 for ITS1 and from 0 to 0.006 for ITS2. Point mutations were common to both spacer regions, but dinucleotide microsatellite repeats were restricted to ITS1. Sequences from neither ITS1 nor ITS2 had a diagnostic distribution or were informative in distinguishing these populations, providing additional support for the status of An. aquasalis as a single species.

Animals↗
PubMedDate not supplied

Cytogenetic and isozyme profile of Sabethes cyaneus: a mosquito of the neotropical canopy.

Sabethes cyaneus, a newly colonized culicine mosquito from the Panamanian forest canopy, has a distribution range from Honduras to Argentina. Cytogenetic studies, the first on any Sabethes species, revealed a karyotype of three pairs of homomorphic chromosomes (2n = 6). Well-developed polytene chromosomes were discovered in the larval salivary glands and a photomap standard was constructed. Clear banding patterns and consistent landmarks distinguished each of the six arms. Substantial asynapsis occurred in the three polytene chromosomes, although the banding pattern of the homologous regions appeared homosequential. A nucleolar organizer was localized in region 5A of the shortest chromosome by the recurrent association of this region with the nucleolus. The large band in region 5A was found heterozygous for width and a deletion. Additional, less conspicuous, polymorphisms for band width and staining intensity were distributed throughout the genome. Biochemical studies of 31 enzyme loci revealed 10 loci to be polymorphic, with an average heterozygosity of 13 percent. Differential expression in developmental stages occurred for 11 loci involving six enzymes.

Animals↗
PubMedDate not supplied

Growth and physiological responses of neotropical mangrove seedlings to root zone hypoxia.

Seedlings of Rhizophora mangle L., Avicennia germinans (L.) Stearn., and Laguncularia racemosa (L.) Gaertn. f. were cultured in aerated or N(2)-purged solution for 12 weeks to assess their relative responses to low oxygen tensions. All three species responded to low oxygen treatment by modifying physiological and morphological patterns to decrease carbon loss by root respiration. However, the extent to which seedling physiology and morphology were altered by low oxygen treatment differed among species. Maintenance of root oxygen concentrations, root respiration rates and root extension rates by R. mangle demonstrated an ability to avoid low oxygen stress with minimal changes in root morphology and physiology. In contrast, oxygen concentrations in A. germinans and L. racemosa roots declined from 16 to 5% or lower within 6 h of treatment. Root hypoxia led to significant decreases in respiration rates of intact root systems (31 and 53% below controls) and root extension rates (38 and 76% below controls) by A. germinans and L. racemosa, respectively, indicating a greater vulnerability of these species to low oxygen tensions in the root zone compared with R. mangle. I conclude that the relative performance of mangrove seedlings growing in anaerobic soils is influenced by interspecific differences in root aeration and concomitant effects on root morphology and physiology.

Journal Article↗
PubMed2000

Seed germination of six mature neotropical rain forest species in response to dehydration.

We studied effects of dehydration and rehydration on germination of seeds of six mature tropical rain forest species-Cupania glabra Swartz, Cymbopetalum baillonii Fries, Poulsenia armata (Miq.) Standl., Stemmadenia donnell-smithii (Rose) Woodson, Rheedia edulis Triana & Planch. and an understory palm Chamaedorea alternans H. Wendl.-from Veracruz, México. Before the seeds were sown, their water content was reduced by 0 (control), 30, 54 and 72% of their original water content. Dehydration affects the ability of seeds to rehydrate, as well as the rate and final percentage of germination when seeds are subsequently rehydrated. Seed survival and germination behavior showed three patterns: (1) C. baillonii, P. armata and S. donnell-smithii had greater tolerance to seed dehydration than C. glabra, C. alternans and R. edulis; (2) partial dehydration enhanced germinability of C. glabra and C. baillonii seeds; and (3) partial dehydration of C. alternans and R. edulis seeds resulted in delayed or sporadic germination. A relationship was found between the effects of dehydration on germination and the seasonality of seed production.

Journal Article↗
PubMed2002

Hydraulic redistribution of soil water by neotropical savanna trees.

The magnitude and direction of water transport by the roots of eight dominant Brazilian savanna (Cerrado) woody species were determined with a heat pulse system that allowed bidirectional measurements of sap flow. The patterns of sap flow observed during the dry season in species with dimorphic root systems were consistent with the occurrence of hydraulic redistribution of soil water, the movement of water from moist to drier regions of the soil profile via plant roots. In these species, shallow roots exhibited positive sap flow (from the soil into the plant) during the day and negative sap flow (from the plant into the soil) during the night. Sap flow in the taproots was positive throughout the 24-h period. Diel fluctuations in soil water potential, with maximum values occurring at night, provided evidence for partial rewetting of upper soil layers by water released from shallow roots. In other species, shallow roots exhibited negative sap flow during both the day and night, indicating that hydraulic redistribution was occurring continuously. A third sap flow pattern was observed at the end of the dry season after a heavy rainfall event when sap flow became negative in the taproot, and positive in the small roots, indicating movement of water from upper soil layers into shallow roots, and then into taproots and deeper soil layers. Experimental manipulations employed to evaluate the response of hydraulic redistribution to changes in plant and environmental conditions included watering the soil surface above shallow roots, decreasing transpiration by covering the plant and cutting roots where probes were inserted. Natural and manipulated patterns of sap flow in roots and stems were consistent with passive movement of water toward competing sinks in the soil and plant. Because dry shallow soil layers were often a stronger sink than the shoot, we suggest that the presence of a dimorphic root system in deciduous species may play a role in facilitating leaf expansion near the end of the dry season when the soil surrounding shallow lateral roots is still dry.

Brazil↗
PubMed2006

Leaf gas exchange characteristics of three neotropical mangrove species in response to varying hydroperiod.

We determined how different hydroperiods affected leaf gas exchange characteristics of greenhouse-grown seedlings (2002) and saplings (2003) of the mangrove species Avicennia germinans (L.) Stearn., Laguncularia racemosa (L.) Gaertn. f., and Rhizophora mangle L. Hydroperiod treatments included no flooding (unflooded), intermittent flooding (intermittent), and permanent flooding (flooded). Plants in the intermittent treatment were measured under both flooded and drained states and compared separately. In the greenhouse study, plants of all species maintained different leaf areas in the contrasting hydroperiods during both years. Assimilation-light response curves indicated that the different hydroperiods had little effect on leaf gas exchange characteristics in either seedlings or saplings. However, short-term intermittent flooding for between 6 and 22 days caused a 20% reduction in maximum leaf-level carbon assimilation rate, a 51% lower light requirement to attain 50% of maximum assimilation, and a 38% higher demand from dark respiration. Although interspecific differences were evident for nearly all measured parameters in both years, there was little consistency in ranking of the interspecific responses. Species by hydroperiod interactions were significant only for sapling leaf area. In a field study, R. mangle saplings along the Shark River in the Everglades National Park either demonstrated no significant effect or slight enhancement of carbon assimilation and water-use efficiency while flooded. We obtained little evidence that contrasting hydroperiods affect leaf gas exchange characteristics of mangrove seedlings or saplings over long time intervals; however, intermittent flooding may cause short-term depressions in leaf gas exchange. The resilience of mangrove systems to flooding, as demonstrated in the permanently flooded treatments, will likely promote photosynthetic and morphological adjustment to slight hydroperiod shifts in many settings.

Avicennia↗
PubMed2006

Antiphonal four-part synchronized chorusing in a Neotropical wren.

Plain-tailed wrens (Thryothorus euophrys) live in groups that sing synchronized choruses, the contributions of females and males alternating with each other in cycles, within which each sex sings two of the four parts, the whole achieving near perfect synchrony. As each bird has a repertoire of ca 20 phrases of each type, the synchrony also requires them to choose the same type at the same time as others of their sex. Songs can last up to 2min, during which individuals join in and drop out. This must be one of the most complex singing performances yet described in a non-human animal.

Animals↗
PubMed2000

Regional endemism and cryptic species revealed by molecular and morphological analysis of a widespread species of Neotropical catfish.

The lower Central American landscape was fully emergent approximately three million years ago, an event which marked the beginning of the Great American biotic interchange. Freshwater fishes participated in the biotic interchange. Because primary freshwater fishes are restricted to freshwater, they provide an excellent system for investigating the interplay of historical and recent processes on the assembly, structure and diversity of the regions' aquatic ecosystems. We focused on examining the history of diversification for a species of catfish (Pimelodella chagresi) whose distribution spans multiple, isolated drainage basins across the Isthmian landscape and into north-western South America. Analysis of mitochondrial DNA haplotypes and morphological traits indicated that P. chagresi, as currently recognized, comprises a species complex. In addition, along the Pacific slope of Panama, repeated dispersion, diversification, extinction and possibly hybridization are thought to underlie a complex distribution of haplotypes. Overall, the results underscore the tremendous importance of historical processes on regional biodiversity.

Animals↗