Patterns of Seed Penetration by the Date Stone Beetle Coccotrypes dactyliperda (Coleoptera, Curculionidae, Scolytinae)

The cryptic spermatophagus date stone beetle (Coccotrypes dactyliperda Fabricius, 1801) tunnels into palm seeds for oviposition and subsequent establishment of brood galleries. Based on behavioral observations this paper describes the biomechanical and gustatory parameters that govern the initial excavation of the tunnels and the subsequent establishment of the galleries. When tunneling into Canary Islands Date Palm (Phoenix canariensis Chabaud, 1882) seeds, penetration principally occurs at the dorsal side of the seed, in particular the groove, which allows the beetle to gain the required traction. Tunneling is executed in a circular fashion with clockwise or counter-clockwise repositioning in approximately one-eighth to one-quarter turns. Biomechanically, the three pairs of legs provide thrust (hind legs), pivoting (mid legs), and lateral control (fore legs). Gustatory cues, the nature of which remains unclear at this point, prevent the beetle from tunneling through to the other side.

Morphophysiological dormancy and germination ecology in diaspores of the subtropical palm Phoenix canariensis Chabaud

The timing of germination is a crucial event in a plant’s life cycle. Seed dormancy and germination mechanisms are important factors regulating seedling emergence. Since detailed experimental evidence for germination pattern of Phoenix canariensis colonizing sub-tropical climate is scarce, we investigated seed dormancy and germination ecology of P. canariensis. We found that the embryo is underdeveloped at the time of dispersal and doubles in size before the cotyledonary petiole (CP) protrudes through the operculum. The primary root and plumule emerge from the elongated CP outside the seed. In light/dark at 30/25°C, the CP emerged from 8% of the diaspores within 30 days and from 76% within 14 weeks. Thus, 8% of the diaspores have MD and the others MPD. Removal of the pericarp and operculum resulted in 100% germination within 5 days in light/dark at 30/25°C. Cold and warm stratification as well as treatment with GA3 significantly increased the germination speed, but the final germination percentage was not significantly increased. Seed germination was synchronized in early summer when seed dormancy was released by cold stratification in the soil over winter. A remote-tubular germination type and intricate root system provide an ecological advantage to the seedling establishment.

Phoenix canariensis (Canary Island date palm).

A datasheet on Phoenix canariensis covering, as an economically important tree, its taxonomy, importance, silviculture, distribution, biology and ecology, uses, products and pests.

Further species within Arecaceae (Palmae; Coryphoideae) to non-native flora of Tunisia and North Africa

Five new alien taxa are here recorded from Tunisia. Reported taxa (Livistona chinensis, Phoenix canariensis, P. reclinata, P. theophrasti and Washingtonia robusta) belong to the subfamily Coryphoideae (Arecaceae). Updated nomenclature, brief descriptions, general and national distributions are provided for each species. Livistona chinensis and Phoenix theophrasti are here reported for the first time in North Africa. Identification keys are also provided.

Germination rates of old and fresh seeds and their implications on invasiveness of the ornamental Canary Islands date palm (Phoenix canariensis)

In many countries, Canary Islands Date Palms (Phoenix canariensis) have escaped their horticulturally managed settings and have commenced to colonise surrounding natural bushland. While dispersed by various vectors, both birds and canids such as foxes, fluctuating environmental conditions may inhibit germination in the season of deposition. The potential of old, previous season’s seeds to germinate when conditions turn favourable has direct implications on the plant’s ability to establish viable, colonising populations. Nothing is known about the ability of older, previous season’s seeds to successfully germinate. Based in experimental data, this paper shows that that the seeds of Phoenix canariensis exhibit both substantial inter-specimen and inter-seasonal variations in their germination potential. The observed variability is caused by the high genetic diversity inherent in a given palm population, as well as by range of environmental factors. At the present stage it is impossible to separate these two. Directions for further research are outlined.

Seed Geometry in the Arecaceae

Fruit and seed shape are important characteristics in taxonomy providing information on ecological, nutritional, and developmental aspects, but their application requires quantification. We propose a method for seed shape quantification based on the comparison of the bi-dimensional images of the seeds with geometric figures. J index is the percent of similarity of a seed image with a figure taken as a model. Models in shape quantification include geometrical figures (circle, ellipse, oval…) and their derivatives, as well as other figures obtained as geometric representations of algebraic equations. The analysis is based on three sources: Published work, images available on the Internet, and seeds collected or stored in our collections. Some of the models here described are applied for the first time in seed morphology, like the superellipses, a group of bidimensional figures that represent well seed shape in species of the Calamoideae and Phoenix canariensis Hort. ex Chabaud. Oval models are proposed for Chamaedorea pauciflora Mart. and cardioid-based models for Trachycarpus fortunei (Hook.) H. Wendl. Diversity of seed shape in the Arecaceae makes this family a good model system to study the application of geometric models in morphology.