Biological Journal of the Linnean Society

Rocamundi, Nicolás; Arce Miller, Marina; Maubecin, Constanza C; Martel, Carlos; Moré, Marcela; Marvaldi, Adriana; Cocucci, Andrea A

doi: 10.1093/botlinnean/boad050pmid: N/A

Flowers of most Piperales do not reward pollinators. However, a few mutualistic pollination relationships have been proposed among the perianth-bearing species. To test the hypothesis of a mutualistic relationship between Prosopanche and beetle pollinators, we studied the pollination biology of three species (P. americana, P. bonacinae, P. panguanensis). For all three species, we recorded flower visitors and flower volatile organic compounds (VOCSs). In addition, for P. americana we investigated flower phases, thermogenesis, visitors’ behaviour, and viability of transported pollen. Using a behavioural experiment, we identified the role of flower heat and fragrance in pollinator attraction. We recorded Neopocadius nitiduloides and Lasiodactylus sp. sap beetles (Nitidulidae) as main pollinators and Hydnorobius hydnorae and H. helleri weevils (Belidae) as occasional pollinators. Thermogenic female flowers heat up to 8°C above the ambient temperature. Flowers only trap the small-sized sap beetles. Methyl-3-methyl-2-butenoate dominated the VOC profile. This was a powerful attractant for sap beetles in controlled bioassays. We conclude that pollination in Prosopanche is mutualistic. This was observed through a pollinator-size-based access limit to the stigmatic chamber and a strong olfactory attractant. Mutualism in Prosopanche therefore contrasts with that of most perianth-bearing Piperales, suggesting it is a novel pollination relationship in early-diverging angiosperms.

Cano, Mauricio J; Ronse De Craene fls, Louis

doi: 10.1093/botlinnean/boad049pmid: N/A

The Primuloid clade or Primulaceae sensus lato is well supported and contains several pollination syndromes, including wind pollination and insect pollination with pollen, nectar, or oil as a reward. Previous studies have recognized two types of nectaries (floral and extrafloral) with different distributions (e.g. ovary, stigma, style, pedicel). This study aimed to reassess the diversity of nectary types, and their distribution and evolution within the clade. Flowers were selected to represent the four subfamilies Maesoideae, Theophrastoideae, Primuloideae, and Myrsinoideae. The flowers were investigated for nectary tissue with electron microscopy, light microscopy, and sugar tests. Nectar is mainly exuded by gynoecial nectarostomata (in Maeseoideae, Theophrastoideae, Primuloideae, and a few basal Myrsinoideae, such as Stimpsonia and Coris) distributed at the base, middle, and top part of the ovary. Myrsinoideae is the exception with an absence of a nectary linked to buzz-pollination, or presenting nectariferous or oil-producing trichomes on the perianth and stamens. The evolution of nectaries is variable in the Primuloid clade, with Primuloideae apparently the starting point of an evolutionary reversal in terms of nectary evolution within this clade, and a high diversity of nectaries within the Myrsinoideae representing various trends that are currently under-investigated. The evolution of floral nectaries in Primulaceae presents an exciting shift from nectar-producing flowers towards a loss of nectaries, and an evolutionary reversal with a shift to the co-option of either oil-producing trichomes or nectar-producing trichomes.

de Deus Vidal, João; Schmitt, Christine B; Koch, Ingrid

doi: 10.1093/botlinnean/boad047pmid: N/A

Brazilian moist forests and savannas are some of the most species-rich biomes in the Neotropics. In the transition zones between these regions, ecotones often accumulate even higher taxonomic diversity. However, whether these ecotonal communities consist of overlapping species widespread from the neighbouring biomes or a specific set of locally adapted species still needs to be clarified. Regional differences in species richness may be influenced by factors such as species' environmental tolerances, life forms, or species’ range sizes. To investigate the species richness found in ecotones, we used the ‘milk-weed’ family (Apocynaceae), which comprises both widespread and narrowly distributed trees, lianas, and shrubs, as a model to evaluate if (i) their observed richness in ecotones is promoted by widespread species or by locally adapted species; (ii) trees, lianas, and shrubs show different richness patterns in savannas, ecotones, and forests; and (iii) species found in ecotones have broader environmental tolerances than other species in the family. We used a taxonomically curated georeferenced dataset to compare the range sizes of 643 species of Apocynaceae from 73 genera listed for Brazil, comprising 298 species with a liana life form and 345 trees, herbs, or shrubs. We recorded 335 predominantly forest species, 56 savanna species, and 152 ecotone species, for which we quantified species richness, areas of occurrence, precipitation, and temperature ranges and tested for differences in range sizes and environmental tolerances between habits and ecoregions. Our results indicate that (i) Apocynaceae species occurring in ecotones have wider geographical ranges than species not occurring in ecotones; (ii) lianas showed higher area-weighted richness in ecotones than other life forms; and (iii) species found in ecotones had broader environmental tolerances than species restricted to moist forests or savannas. These results indicate that the species richness found in ecotones between savannas and moist forests in Brazil is not necessarily a consequence of higher endemism and local adaptation but may also be a result of overlapping ranges of widespread species typically associated with neighbouring biomes. Together, our findings add to our understanding of ecotones and biomes as continuous, gradual biogeographical transitions instead of sharply defined ecological units.

Choi, Bokyung; Duretto, Marco F; Hong, Suk-Pyo

doi: 10.1093/botlinnean/boad055pmid: N/A

The Eriostemon–Phebalium clade (Rutaceae) includes c. 200 species across 16 genera, and is distributed in Australia (including Tasmania), New Caledonia, New Hebrides, New Zealand, and New Guinea. Phylogenetic analyses based on DNA sequences have consistently shown that the Eriostemon–Phebalium group is robustly monophyletic. However, despite this, taxonomy within the group is still uncertain: relationships between the genera are not well understood, and the genus Philotheca is polyphyletic. Seed morphological characters can be useful in taxonomy in angiosperms, and in this study, 21 seed morphological characters for 29 taxa of all the 16 genera circumscribed in the Eriostemon–Phebalium clade were examined using stereo and scanning electron microscopy. Seed morphological traits such as testa type and hilum were informative for some of the robustly supported clades in molecular phylogenetic studies, and a combination of seed characters could be useful for species identification. This study highlights the potential of seed morphological traits for the systematics.

Barrios-Leal, Dora Yovana; Menezes, Rodolpho S T; Zappi, Daniela; Manfrin, Maura Helena

doi: 10.1093/botlinnean/boad054pmid: N/A

The Caatinga biogeographical region, located in the semi-arid region of northeastern Brazil, is characterized by high levels of cactus diversity and endemism. In this study, we investigated the genetic diversity, differentiation, and phylogeography of three Tacinga species (Tacinga inamoena, Tacinga subcylindrica, and Tacinga palmadora), which are endemic and widely distributed in the Caatinga. We collected 222 samples from 108 locations and used plastid (3ʹrps16-5ʹtrnK, PsbE-PetL) and nuclear (PhyC) molecular markers for a multilocus approach. Our results suggest that diversification of the three Tacinga species occurred during the middle Pleistocene, with the Southern Sertaneja Depression ecoregion of the Caatinga being identified as the ancestral area. Interestingly, analyses of genetic structure did not show any evidence that the major river in the region (the Sao Francisco River) and the Caatinga ecoregions acted as biogeographical barriers for gene flow in these species. This suggests that the three Tacinga species exhibited different responses to widely accepted geographical and geomorphological barriers known to affect other taxonomic groups in the Caatinga. Overall, our findings provide new insights into the biogeographical history of the Caatinga and the factors that have shaped diversification and genetic structure of species in this region. Our study underlines the importance of considering the unique natural history and biological characteristics of individual taxonomic groups when investigating the biogeography of the Caatinga.

Zavialov, Alexander E; Remizowa, Margarita V

doi: 10.1093/botlinnean/boad048pmid: N/A

Acer negundo L. is a wind-pollinated, dioecious tree that occasionally produces flowers with rudiments of the opposite sex. Both the male (staminate) and female (pistillate) flowers possess only two whorls: sepals and stamens or carpels, the arrangement of which is disputed. Here we present data on inflorescence and floral development, pollen fertility in staminodes and the diversity of male and female flowers. We found that the merism of male flowers is unstable, and the numbers of stamens and sepals vary independently. The different floral groundplans always occur within the inflorescences of the same generative shoot. The development of a flower begins with the initiation of sepals, but in female flowers, sepals are initiated sequentially and remain of different sizes, whereas in male flowers, sepals are initiated almost simultaneously and are equal. After the appearance of stamen primordia or carpel primordia, a part of the undifferentiated meristem remains. This unused meristem can be involved in producing staminodes or pistillodia. Both unisexual and (partly) bisexual flowers are found in the same inflorescence. Staminodes are either completely sterile or produce some amount of viable pollen. These features indicate the possibility of functional bisexuality in A. negundo.