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PREMISE: Wood density is a crucial plant functional trait related to plant life history strategies. Its ecological importance in small-stature growth forms (e.g., shrubs) has not been extensively examined. Given that hydraulic conduit dimensions vary positively with plant height and that there is a negative relationship between conduits' diameter and wood density, I hypothesized an also negative relationship between wood density and plant height. Knowing that bark and pith proportions are significant in small-diameter stems, I additionally disentangled the contribution of wood, bark, and pith to stem density. METHODS: I determined density in small-diameter stems across 153 species spanning all major angiosperm and gymnosperm orders by considering a diversity of growth forms (trees, treelets, shrubs, vines, and hemiparasites). Stem cross sections were dissected to consider the densities of wood with bark and pith; wood with pith and without bark; wood with bark and no pith; and wood without bark and pith. Secondary growth was also measured. RESULTS: Trees showed similar wood densities as non-self-supporting vines, and both showed significantly less dense wood than treelets, shrubs, and hemiparasites. General comparisons showed that wood was significantly denser than all other tissues, and these differences did not depend on growth form. Wood density was significantly and negatively related to growth rate and pith area proportions but not to bark thickness proportion. CONCLUSIONS: An implicit negative relationship between maximum plant height and stem density emerges as a property of plants likely linked to hydraulic conductive size.

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Mechanisms to detoxify aluminium (Al) is a hot topic for cultivated plants. However, little information is known about the mechanisms used by native plants to deal with Al-toxicity. In Cerrado, some generalist mistletoe species, such as Passovia ovata (Pohl ex DC.) Kuijt and Struthanthus polyanthus Mart. can parasitize Al-accumulating and Al-excluding plant species without any clear symptoms of toxicity and mineral deficiency, while Psittacanthus robustus (Mart.) Marloth, a more specialist mistletoe, seems to be an Al-dependent species, parasitizing only Al-accumulating hosts. Here we (i) characterized the forms and compartmentalization of Al in leaves of P. robustus; (ii) compared Ca and Al leaf concentration, and leaf concentration of organic acids and polyphenols between facultative Al-accumulating (P. ovata and S. polyanthus) and Al-dependent (P. robustus) mistletoe species infecting Miconia albicans (Sw.) Steud. (Al-accumulating species). P. robustus chelated Al3+ with oxalate and stored it in the phloematic and epidermic leaf tissues. Leaf Ca and Al concentration did not differ among species. Leaf oxalate concentration was higher in the Al-dependent species. Concentrations of citrate and phenolic compounds were higher in the leaves of the facultative Al-accumulating species. These results show that facultative Al-accumulating and Al-dependent species use different mechanisms to detoxify Al. Moreover, this is the first report on a mistletoes species (P. robustus) with a potential calcifuge behaviour in Cerrado.

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BACKGROUND: Relationships between floral biology and pollinator behavior are important to understanding species diversity of hemiparasitic Psittacanthus mistletoes (c. 120 species). We aimed to investigate trait divergence linked to pollinator attraction and reproductive isolation (RI) in two hummingbird-pollinated and bird-dispersed Psittacanthus species with range overlap. METHODS: We investigated the phylogenetic relationships, floral biology, pollinator assemblages, seed dispersers and host usage, and the breeding system and female reproductive success of two sympatric populations of P. calyculatus and P. auriculatus, and one allopatric population of P. calyculatus. Flowers in sympatry were also reciprocally pollinated to assess a post-mating component of RI. RESULTS: Hummingbird assemblages differed between calyculatus populations, while allopatric plants of calyculatus opened more but smaller flowers with longer lifespans and produced less nectar than those in sympatry. Bayesian-based phylogenetic analysis indicated monophyly for calyculatus populations (i.e. both populations belong to the same species). In sympatry, calyculatus plants opened more and larger flowers with longer lifespans and produced same nectar volume than those of auriculatus; populations shared pollinators but seed dispersers and host usage differed between species. Nectar standing crops differed between sympatric populations, with lower visitation in calyculatus. Hand pollination experiments indicated a predominant outcrossing breeding system, with fruit set after interspecific pollination two times higher from calyculatus to auriculatus than in the opposite direction. CONCLUSIONS: Given the low genetic differentiation between calyculatus populations, observed trait divergence could have resulted from changes regarding the local communities of pollinators and, therefore, expected divergence for peripheral, allopatric populations. Using RI estimates, there were fewer heterospecific matings than expected by chance in P. calyculatus (RI4A = 0.629) as compared to P. auriculatus (RI4A = 0.20). When considering other factors of ecological isolation that affect co-occurrence, the RI4C values indicate that isolation by hummingbird pollinators was less effective (0.20) than isolation by host tree species and seed dispersers (0.80 and 0.60, respectively), suggesting that host usage is the most important ecological isolation factor between the two species. Accordingly, the absolute and relative cumulative strength values indicated that the host tree species' barrier is currently contributing the most to maintaining these species in sympatry.

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The family Loranthaceae Juss., characterized by its parasitic habit, is rarely studied in Brazil. Current research provides a taxonomic survey of Loranthaceae in the State of Paraiba, northeastern Brazil, in which ten species belonging to four genera have been recorded: Passovia (one species), Psittacanthus (two species), Pusillanthus (one species) and Struthanthus (six species). Struthanthus concinnus Mart. was found for the first time in the state of Paraíba. A key to the species identification and taxonomic descriptions is presented, with images, geographic distribution and host data.

A família Loranthaceae Juss. é caracterizada pelo hábito parasítico e é ainda escassamente estudada no Brasil. Este trabalho realizou o levantamento taxonômico de Loranthaceae no Estado da Paraíba, nordeste do Brasil, onde dez espécies pertencentes a quatro gêneros foram registradas: Passovia (1 espécie), Psittacanthus (2 espécies), Pusillanthus (1 espécie) e Struthanthus (6 espécies). Struthanthus concinnus Mart. foi registrada pela primeira vez para a flora do Estado da Paraíba. Uma chave para a identificação das espécies e descrições taxonômicas é apresentada, com imagens, dados de distribuição geográfica e de hospedeiros também fornecidos.

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RESUMO

The family Loranthaceae Juss., characterized by its parasitic habit, is rarely studied in Brazil. Current research provides a taxonomic survey of Loranthaceae in the State of Paraiba, northeastern Brazil, in which ten species belonging to four genera have been recorded: Passovia (one species), Psittacanthus (two species), Pusillanthus (one species) and Struthanthus (six species). Struthanthus concinnus Mart. was found for the first time in the state of Paraíba. A key to the species identification and taxonomic descriptions is presented, with images, geographic distribution and host data.

A família Loranthaceae Juss. é caracterizada pelo hábito parasítico e é ainda escassamente estudada no Brasil. Este trabalho realizou o levantamento taxonômico de Loranthaceae no Estado da Paraíba, nordeste do Brasil, onde dez espécies pertencentes a quatro gêneros foram registradas: Passovia (1 espécie), Psittacanthus (2 espécies), Pusillanthus (1 espécie) e Struthanthus (6 espécies). Struthanthus concinnus Mart. foi registrada pela primeira vez para a flora do Estado da Paraíba. Uma chave para a identificação das espécies e descrições taxonômicas é apresentada, com imagens, dados de distribuição geográfica e de hospedeiros também fornecidos.

Assuntos

RESUMO

The family Loranthaceae Juss., characterized by its parasitic habit, is rarely studied in Brazil. Current research provides a taxonomic survey of Loranthaceae in the State of Paraiba, northeastern Brazil, in which ten species belonging to four genera have been recorded: Passovia (one species), Psittacanthus (two species), Pusillanthus (one species) and Struthanthus (six species). Struthanthus concinnus Mart. was found for the first time in the state of Paraíba. A key to the species identification and taxonomic descriptions is presented, with images, geographic distribution and host data.(AU)

A família Loranthaceae Juss. é caracterizada pelo hábito parasítico e é ainda escassamente estudada no Brasil. Este trabalho realizou o levantamento taxonômico de Loranthaceae no Estado da Paraíba, nordeste do Brasil, onde dez espécies pertencentes a quatro gêneros foram registradas: Passovia (1 espécie), Psittacanthus (2 espécies), Pusillanthus (1 espécie) e Struthanthus (6 espécies). Struthanthus concinnus Mart. foi registrada pela primeira vez para a flora do Estado da Paraíba. Uma chave para a identificação das espécies e descrições taxonômicas é apresentada, com imagens, dados de distribuição geográfica e de hospedeiros também fornecidos.(AU)

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