Isoetes tamaulipana Mora-Olivo, A.Mend. & Mart.-Aval.
Descripción
Isoetes tamaulipana is most similar to I. mexicana in length, width and color of leaves, but differs in having rootstocks 3 to 4 lobed (vs. 2 lobed in I. mexicana) and a velum covering 3/4 of the sporangium (vs. covering 1/3 of the sporangium). It further differs from this and other species in having light brown or greyish megaspores with a smooth to rugulate perispore and thin laesural walls, laesurae and proximal face of the equatorial ridge bearing tiny spines, and microspores being grey and echinate (vs. megaspores white to pale grey, smooth to weakly tuberculate, microspores grey and tuberculate-verrucose in I. mexicana and other similar species).
Perennials; aquatic plants rooted in substrate with emergent leaves; rootstock semi-globose, 3–4 lobed, 10–25 mm wide, 6–10 mm tall, without scales, leaves 15–30 per plant, erect and compactly arranged, 15–25 cm long, 3.5–6 mm wide at the base, 1.5–2 mm wide at the half the length, sub-terete in transversal section, basal part with hyaline alae, tapering to the apex, flexible, green when fresh or yellowish when dried; sporangia with translucent walls, globose or elliptical to obovate in the adaxial face, velum covering 75% of the macrosporangium, and 40% of the microsporangium, ligulae triangular and membranaceous; megasporangia white when fresh or pale brown when dried; microsporangia dark colored when fresh or greyish when dried. Megaspores tetrahedral, trilete, 380–400 µm in diameter, light brown to greyish, proximal and distal face smooth or slightly wavy; length of the lasural arms 0.22–0.26 µm, laesural arms 18–25 µm wide, 15–20 µm tall, with tiny spines besides the laesurae and proximal to the equatorial ridge; equatorial ridge 18–20 µm wide. Microspores bilateral, cristate to echinate, greyish in mass, 27–30 µm long, 17–20 µm wide.
Etymology:—Epithet refers to the Mexican state where the species was discovered.A
Perennials; aquatic plants rooted in substrate with emergent leaves; rootstock semi-globose, 3–4 lobed, 10–25 mm wide, 6–10 mm tall, without scales, leaves 15–30 per plant, erect and compactly arranged, 15–25 cm long, 3.5–6 mm wide at the base, 1.5–2 mm wide at the half the length, sub-terete in transversal section, basal part with hyaline alae, tapering to the apex, flexible, green when fresh or yellowish when dried; sporangia with translucent walls, globose or elliptical to obovate in the adaxial face, velum covering 75% of the macrosporangium, and 40% of the microsporangium, ligulae triangular and membranaceous; megasporangia white when fresh or pale brown when dried; microsporangia dark colored when fresh or greyish when dried. Megaspores tetrahedral, trilete, 380–400 µm in diameter, light brown to greyish, proximal and distal face smooth or slightly wavy; length of the lasural arms 0.22–0.26 µm, laesural arms 18–25 µm wide, 15–20 µm tall, with tiny spines besides the laesurae and proximal to the equatorial ridge; equatorial ridge 18–20 µm wide. Microspores bilateral, cristate to echinate, greyish in mass, 27–30 µm long, 17–20 µm wide.
Etymology:—Epithet refers to the Mexican state where the species was discovered.A
Forma de vida
Hidrófita enraizadaA
Distribución
México (país): Tamaulipas EndémicoA
Elevación
1071 mA
Categoría IUCN
No incluidaB
Categoría NOM-059-SEMARNAT-2010
No incluidaC
Discusión taxonómica
Isoetes tamaulipana is the first record for the family Isoetaceae in the state of Tamaulipas and is the only known species from northeastern Mexico (Mora-Olivo & Villaseñor 2007). It is important to point out that plants of Isoetes are always associated with moist environments and only a few species grow in seasonal ponds in basaltic or granitic outcrops. The flora that develops in this type of substrate has been widely studied in the United States of America (Singhurst et al. 2011) and several species of Isoetes are associated with these habitats such as I. melanospora Engelmann (1878: 1), I. tegetiformans Rury (1978: 108), and I. piedmontana (Pfeiffer 1939: 411) Reed (1965: 392) (Heafner & Bray, 2005, Brunton & Britton 2006, Singhurst et al. 2011). However, I. orcuttii Eaton (1900: 13) from Baja California is the only species known in Mexico previously known from this kind of habitat.
The new species is easily distinguished by its light brown or greyish megaspores with a smooth or slightly wavy exospore, thin laesure, laesure and proximal face of the cingulum with tiny spines (perispore), and microspores that are grey and echinate. Because of its restricted distribution and its specialized aquatic habitat, Isoetes tamaulipana might be considered an endangered or vulnerable species. Future plans to implement a Natural Protected Area at the Cerro El Diente in Sierra de San Carlos, Tamaulipas could help to conserve and protect this and other species in the area.
A
The new species is easily distinguished by its light brown or greyish megaspores with a smooth or slightly wavy exospore, thin laesure, laesure and proximal face of the cingulum with tiny spines (perispore), and microspores that are grey and echinate. Because of its restricted distribution and its specialized aquatic habitat, Isoetes tamaulipana might be considered an endangered or vulnerable species. Future plans to implement a Natural Protected Area at the Cerro El Diente in Sierra de San Carlos, Tamaulipas could help to conserve and protect this and other species in the area.
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