Alejandra V. González

IDENTIFICATION OF CRYPTIC SPECIES IN THE LESSONIA NIGRESCENS COMPLEX (PHAEOPHYCEAE, LAMINARIALES)1

The kelp Lessonia nigrescens Bory is the most ecologically and economically important seaweed in rocky intertidal and shallow subtidal habitats along the temperate Pacific South American coasts. Recent molecular studies suggest the existence of two lineages, one (northern lineage) from 17° S to 30° S and a second (central lineage) from 29° S to 41° S. To identify and name these lineages we performed morphological, nomenclatural and field studies. Four external and three internal anatomical traits permitted a morphological separation of the two lineages. The internal structure of both lineages was different from the isolectotype of Lessonia nigrescens. It is therefore concluded that the name Lessonia nigrescens should not be used for the Chilean material. Chordaria spicata Suhr appears as the oldest available name for the central lineage, while Lessonia berteroana Montagne is the oldest name for the northern lineage. In both cases, the type material consisted of small‐sized, apical branches of larger plants. The new combination Lessonia spicata (Suhr) Santelices is proposed for the central lineage and we reinstate Lessonia berteroana for the northern lineage. Laminaria scissa Suhr is reduced to synonym of L. spicata. Representative specimens of Lessonia nigrescens were not found during new visits to its type locality in Cape Horn and along Chile. Future studies should verify the status of this species.

Floral Herbivory Affects Female Reproductive Success and Pollinator Visitation in the Perennial Herb Alstroemeria ligtu (Alstroemeriaceae)

Floral damage can reduce flower attractiveness for pollinator service. However, the reproductive impact of flower herbivory may be contingent on a petal that is damaged. Flowers having nectar guides are expected to suffer reduction in reproductive success when damage is concentrated on these structures compared to petals less involved in pollinator attraction. In this study, we recorded the reflectance pattern of distinctive yellow tepals of Alstroemeria ligtu and examined their functional role for pollinator attraction and reproductive success. We quantified the richness and abundance of pollinator species attracted to flowers and estimated fruit set and seed production in flowers subject to (1) nectar guide removal, (2) lateral red tepal removal, and (3) unmanipulated flowers. Results indicate that nectar guide removal reduced pollinator visitation rate but did not affect community-level descriptors such as pollinator species richness and flower diversity. The reduction in visitation rate translated into a reduced fruit set and seed production, hence confirming that nectar guides have a clear functional role in the pollination process. We conclude that the location where damage occurs is a relevant factor for pollinator attraction and subsequent reproductive success in this species, suggesting that nectar guide damage may disrupt fine-tuned plant-pollinator communication systems.

Pollen Limitation and Reproductive Assurance in the Flora of the Coastal Atacama Desert

Pollen limitation (PL) in plant populations is supposed to be particularly strong in variable pollinator environments. Here, we examined the extent of PL in the coastal Atacama Desert, where low and unpredictable rainfall drives large interannual variation in plant cover and pollinator abundances. We estimated PL levels and the capacity for autonomous selfing (autofertility) in 16 annual and perennial species. In addition, we compared fruit set of emasculated and intact flowers to test whether selfing provides reproductive assurance. We also examined the relationships between autofertility and life forms, between PL and autofertility, and between PL and flower size. We found a low level of PL ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Morphological convergence in the inter-holdfast coalescence process among kelp and kelp-like seaweeds (Lessonia, Macrocystis, Durvillaea)

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Floral integration and pollinator diversity in the generalized plant-pollinator system of Alstroemeria ligtu (Alstroemeriaceae)

\end{document} ) and a high incidence of autofertility, which was negatively correlated with PL and closely related to life form. Our results suggest that the low PL levels in autonomous‐selfing species result from the reproductive assurance provided by selfing. Considering nonautonomous species only, the mean PL (0.44) was similar to that reported for other habitats. We detected no association between PL and flower size. In summary, high rates of PL were not a general pattern among plants in the Atacama Desert. The low levels of PL can be attributed to the high incidence of autofertility.

Temporal and spatial variation of the pollinator assemblages in Alstroemeria ligtu (Alstroemeriaceae)

Coalescing macroalgae may fuse with conspecifics, forming genetically heterogeneous entities known as chimera. This process has been shown in taxa from roughly half the red algal orders and in the Codium species, a green alga. Field observations indicate that common and dominant kelps along central Chile exhibit a fused holdfast. We evaluated whether such fusions are true coalescence processes in Lessonia spicata and Lessonia berteroana. To this end, we characterized the ultrastructural event involved in holdfast fusion in the laboratory. Additionally, coalescence in natural populations was quantified by measuring the frequency of individuals with genetically heterogenic stipes within the same holdfast. Results indicate that coalescence appears as a frequent process in laboratory, mostly restricted to intraspecific fusions. During fusion, the meristodermatic cells located in the contact area modify their morphology and reduce the number of plastids, mitochondria, and cell inclusions. The cell wall becomes much thinner and develops plasmodesmata, enhancing communication with equivalent cells of the other coalescencing individual. Stipe genotyping indicates that there is a widespread occurrence of chimerism in both species and genetic heterogeneity is increasing directly with the increasing number of stipes. The combination of results suggests that kelp frequently coalesce in the field, and the histological response observed approaches that of red algae. Since kelps are part of the dominant vegetation in low intertidal and shallow subtidal beds, the adaptive values of coalescence in these species should be evaluated. It is concluded that coalescence and chimerism are evolutionary convergent processes, occurring in all three major groups of seaweeds.

Pollination and breeding system in Adesmia bijuga Phil. (Fabaceae), a critically endangered species in Central Chile

Abstract: In brown macroalgae, intraspecific holdfast coalescence has only been studied in two species of Lessonia (Lessonia spicata and Lessonia berteroana). In both species coalescence followed the same general pattern: once the connection between holdfasts was established, the contact areas showed significant cellular morphological modifications. Typical epidermal cells became polygonal and similar to cortical cells. In addition, coalescence involved the de novo formation of secondary plasmodesmata, establishing a direct cytoplasm connection within neighbouring cells, where dense materials, vacuoles and organelles can be observed. In the present study, we demonstrate intraspecific holdfast coalescence in two additional kelp species, Lessonia trabeculata and Macrocystis pyrifera, as well as in the kelp-like seaweed, Durvillaea antarctica. The process of holdfast fusions in these species is similar to that described previously and suggests that this is a generalized phenomenon among kelp and kelp-like brown algae. In addition, the formation of cytoplasmic connections between genetically different brown algal individuals is shown for the first time.

Testing the effects of heterozygosity on growth rate plasticity in the seaweed Gracilaria chilensis (Rhodophyta)

Los polinizadores son capaces de discriminar entre diferentes fenotipos florales. Por lo tanto, flores mas atractivas para los polinizadores usualmente reciben mas visitas a sus estructuras reproductivas. Sin embargo, este efecto de atraccion no ocurre necesariamente de una forma binaria, todo o nada. Loasa tricolor KerGawl. es una hierba anual cubierta con pelos urticantes. Sus flores presentan una corola con cinco petalos amarillos y escamas nectarinas rojas. En este estudio, evaluamos si la variacion en el fenotipo floral de L. tricolor afecta la discriminacion por polinizadores, siguiendo una respuesta de tipo dosis-dependiente. Este estudio fue llevado a cabo en un area protegida de Chile donde L. tricolor muestra altos niveles de herbivoria floral, probablemente afectando su atraccion hacia los polinizadores. Modificamos experimentalmente el fenotipo de la corola, removiendo tres o todos sus petalos. Medimos la tasa de visita, riqueza y diversidad de especies de polinizadores en las flores tratadas y control. Nuestros resultados muestran que la remocion de tres petalos no reduce la tasa de visita comparado con el control, mientras que la remocion de todos los petalos reduce significativamente la tasa de visita. La mayoria de las especies de polinizadores fueron registradas en el tratamiento de remocion de tres petalos (nueve especies), mientras que en el tratamiento de remocion de todos los petalos se obtuvo un bajo valor de riqueza (cuatro especies). Estos resultados sugieren que la diversidad, riqueza y tasa de visita de las especies son afectadas por la variacion en el fenotipo floral, pero probablemente solo por la perdida completa de petalos. Nosotros sugerimos que los diferentes niveles de herbivoria floral en L. tricolor no afectan la discriminacion de los polinizadores en forma dosis-dependiente.