Phylogenetic Relationships of Tovomita (Clusiaceae): Carpel Number and Geographic Distribution Speak Louder than Venation Pattern

Abstract—Tovomita is a Neotropical clade of Clusiaceae that includes 52 species widely distributed throughout the Amazon, Atlantic, Antilles, and Chocoan/southern Mesoamerican rainforests. Species-level relationships within Tovomita remain largely unexplored, thus hindering our understanding of their biogeography and the evolution of key morphological characters in the genus. Here, we inferred a plastid genome phylogeny containing 18 Tovomita species using maximum likelihood and Bayesian inference approaches. Our results indicate that current infrageneric classification of Tovomita, which relies largely on leaf venation, does not reflect phylogenetic relationships. Instead, we identify carpel number as a more reliable morphological trait for infrageneric classification: clades within Tovomita tend to include species that possess either four or five (or more) carpels. Moreover, groups of species within Tovomita tend to exhibit a high degree of geographic endemicity corresponding to their clade affiliation: species within these clades are restricted to either Amazon or Atlantic forests. The well supported clade of Atlantic forest inhabitants we identify is sister to a clade of mostly Amazonian species that also includes Amazon and Atlantic forest disjunct species, which are more closely related to Amazonian than to other Atlantic forest species. These findings represent a first important step in elucidating morphological evolution and biogeography in this widespread genus of neotropical rainforest trees and shrubs.

Influencia del genotipo y la temperatura sobre la carpelodia en papaya

Carpellody is a phenomenon that affects hermaphrodite flowers of papaya, and consists in the transformation of the stamens into additional carpels, resulting in ovary malformation that consequently affects fruit shape and diminishes its market value. The objective of this study was to quantify the incidence of flower carpellody in papaya, and the effect of temperature on this phenomenon. An experiment was carried out between October of 2006 and January of 2007 at ”Los Diamantes” Agricultural Experiment Station, located in the province of Limón. Four breeding lines and four experimental hybrids were arranged in a randomized complete block design with four replications. The analyzed variables were the carpel number for ovaries of hermaphrodite flowers and the daily temperature during a 60-day period prior to floral anthesis of each evaluated flower. The carpel number of lines and hybrids differed significantly each week (p≤0,03). Line and hybrid averages also differed significantly during the twelve-week period (p<0,0001). The cross between a strong carpellodic line and a stable or a weak female-sterile line resulted in a hybrid that exhibited carpellody, which suggests that carpellody is dominant. The correlation between carpel number and temperature suggests that the amplitude of temperature fluctuations during the day was a determinant factor in the induction of carpellody.

Variations with altitude in reproductive traits and resource allocation of three Tibetan species of Ranunculaceae

We investigated the adaptive response of alpine plants to elevational gradients by examining reproductive traits and resource allocation of three species of Ranunculaceae with contrasting mating systems in alpine and subalpine populations on the eastern QinhaiTibetan Plateu. The results showed that (i) at alpine sites, the self-incompatible Trollius ranunculoides Hemsley tended to become limited by pollination rather than by nutrient availability, although the self-compatible Anemone rivularis var. flore-minore Maxim. Fl. Tang. and A. obtusiloba D.Don. seemed not to be limited by pollen availability; (ii) influences on the reproduction of these three species induced by high altitude were seen in different reproductive characters, and the influences were, to some extent, dependent on the plant. Female investment in the self-compatible A. rivularis and A. obtusiloba was influenced by altitude and plant size; with a much lower carpel number per flower and larger mean seed size in A. rivularis, and a much higher carpel number per flower and smaller mean seed size in A. obtusiloba, at a higher altitude. Floral investment in the self-incompatible T. ranunculoides was also influenced by altitude and plant size, with a smaller single-flower size and larger seed at the higher altitude. Results also showed that (iii) reproductive allocation to flowering and fruiting did not always decrease with altitude as predicted. This may be due to higher nutrient availability in soil at alpine sites. (iv) Although self-pollination may be an assurance mechanism alleviating pollination limitation, changes in allocation pattern, (i.e. the male-biased floral sexual allocation in A. rivularis and the higher allocation to attractive structure in A. obtusiloba) seem to promote pollinator visits at the high altitude.

Dissecting the Genetic Pathway to Extreme Fruit Size in Tomato Using a Cross Between the Small-Fruited Wild Species Lycopersicon pimpinellifolium and L. esculentum var. Giant Heirloom

In an effort to determine the genetic basis of exceptionally large tomato fruits, QTL analysis was performed on a population derived from a cross between the wild species Lycopersicon pimpinellifolium (average fruit weight, 1 g) and the L. esculentum cultivar var. Giant Heirloom, which bears fruit in excess of 1000 g. QTL analysis revealed that the majority (67%) of phenotypic variation in fruit size could be attributed to six major loci localized on chromosomes 1-3 and 11. None of the QTL map to novel regions of the genome—all have been reported in previous studies involving moderately sized tomatoes. This result suggests that no major QTL beyond those already reported were involved in the evolution of extremely large fruit. However, this is the first time that all six QTL have emerged in a single population, suggesting that exceptionally large-fruited varieties, such as Giant Heirloom, are the result of a novel combination of preexisting QTL alleles. One of the detected QTL, fw2.2, has been cloned and exerts its effect on fruit size through global control of cell division early in carpel/fruit development. However, the most significant QTL detected in this study (fw11.3, lcn11.1) maps to the bottom of chromosome 11 and seems to exert its effect on fruit size through control of carpel/locule number. A second major locus, also affecting carpel number (and hence fruit size), was mapped to chromosome 2 (fw2.1, lcn2.1). We propose that these two carpel number QTL correspond to the loci described by early classical geneticists as fasciated (f) and locule number (lc), respectively.