Habitat differentiation and geographic separation of Isoetes velata populations in central Iberian Peninsula

José Antonio Molina

doi:10.5209/bocm.75525

Abstract

Populations of Isoetes velata were studied in order to provide more information on their habitat and distribution in the Western and Northwestern Iberian Peninsula. Habitat together with morphology of megaspores were used as diagnostic features. The form I. velata subsp. velata f. lereschii is considered here as a synonym of I. velata subsp. asturicense and therefore only two taxa remain within the species: I. velata subsp. velata and I. velata subsp. asturicense. Intermediate individuals have been found in the Western Central System. The differentiation within the I. velata group appears to be the result of gradual genetic divergence after isolation. Palaeobotanical data confirm the presence of I. velata subsp. asturicense in Late Glacial lake sediments in northwestern Spain. Cluster classification of the soft-water vegetation with Isoetes velata subsp. asturicense revealed two main groups in the Spanish Central System. A single association, the Sparganio angustifolii-Callitrichetum fontqueri which includes Iberian Atlantic stands of Sparganium angustifolium and Isoetes velata subsp. asturicense, is here recognized. Besides, a variant of the association with Eleocharis acicularis is identified in shallow temporary waters in the Western Sierra de Gredos.

Highlights

Isoetes velata/longissima group is a species complex in which genetic investigations could probably clarify the taxonomy of the including taxa (Troia & Rouhan 2018)
Braun in Bory & Durieu has the highest infra-specific diversity in Europe (Derrick et al 1987). Within this taxon two subspecies have been described in the Iberian Peninsula (Prada 1986): I. velata subsp. velata and I. velata subsp. asturicense (Laínz) Rivas-Martínez & Prada, both of them with the lowest chromosome number found in the genus (2n=22)
The Late Glacial megaspores from Sierra de Queixa-Manzaneda (1360 m) appeared smooth and were 300-360 μm in diameter. All these populations are assigned to Isoetes velata subsp. asturicense, and this taxon shows higher megaspore variability than hitherto known

Summary

Introduction

Isoetes velata/longissima group is a species complex in which genetic investigations could probably clarify the taxonomy of the including taxa (Troia & Rouhan 2018). Braun in Bory & Durieu has the highest infra-specific diversity in Europe (Derrick et al 1987). Within this taxon two subspecies have been described in the Iberian Peninsula (Prada 1986): I. velata subsp. This taxon has been characterized by small leaves (from 5 to 15 cm) with few fibrous subepidermic fascicles, thin cell walls and few stomata. Their megaspores are ornamented with sharp tubercles (Rivas-Martínez et al 1982)

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Conclusion