Jodina rhombifolia subsp. delasotae, Arana & Luna, 2019

Arana, Marcelo D. & Luna, María Luján, 2019, A new subspecies of Jodina rhombifolia (Santalales: Cervantesiaceae), with taxonomical considerations, Phytotaxa 425 (4), pp. 208-218 : 210

Jodina rhombifolia subsp. delasotae , new subspecies

As previously pointed out, published observations on variation within Jodina refer particularly to vegetative, specifically foliar, features. However, many of the published illustrations do not show sufficient detail or are difficult to compare because of the halftone resolution or because of the poor quality of early photographs. From detailed morphological and anatomical features first observed by Luna & de la Sota (2003) and corroborated here by comparison with material of known origin from the complete area of distribution, it can be concluded that some morphological and anatomical features are correlated with the geographic distribution. Plants with dorsiventral mesophyll, stomata present only on the abaxial epidermis (“patrón A” from Luna & de la Sota, 2003), 4- and 5-merous flowers in proportion 50–50 and glandular disk with obtuse, rounded lobes dark green occur in the easternmost part of the range, entirely in the Pampean biogeographic province, in Southern Brazil, Uruguay and eastern Argentina (east of Entre Rios and Buenos Aires), whereas plants with isobilateral mesophyll, stomata on both epidermis surfaces (“patrón B” from Luna & de la Sota), 4- and 5-merous flowers in proportion 0 (10)–90 (100) and glandular disk with acute lobes light green also grow in the Pampean biogeographic province, but in the Espinal district, and also in the western part of the entire range, in Southern Bolivia and northern and central Argentina ( Figs. 2 and 3 ). The discovery of geographical and habitat-related patterns in distribution of related taxa could therefore uncover as-yet-unknown pockets of endemism and diversity that might warrant reconsideration for particular habitats or sites for conservation of different lineages, especially in the highly degraded Pampean habitats. The morphological and anatomical differences observed, strongly correlated with the well-delimited geographical distribution patterns ( Fig. 3 ), suggest the recognition of two distinguishable subspecific entities within Jodina rhombifolia, (Hamilton & Reichard 1992) .

The name published by Hooker & Arnott (1832) is based on specimens from both areas where the distinguishable patterns occur (San Luis, in central Argentina, and Uruguay), but as the lectotype selected here falls within the geographical range of the plants belonging to “pattern B” of Luna & de la Sota (2003), it seems more advisable to propose a new subspecies name based on a different type, with dorsiventral mesophyll, stomata present only on the abaxial epidermis, corresponding to “patrón A” of Luna & de la Sota (2003), usually almost all flowers 5-merous and glandular disk with rounded, obtuse lobes light green lobes.

Figures

FIGURE 2. Leaf anatomy of the two subspecies of Jodina rhombifolia. A–B, E. J. rhombifolia subsp.rhombifolia. A–B. SEM micrographs illustrating stomata on the adaxial (A) and abaxial (B) leaf surfaces (arrows). Rhombic crystals of calcium oxalate are indicated in B (arrowheads). E. Light micrograph of transverse section showing isobilateral mesophyll and stomata on both epidermal surfaces (arrows). C–D, F. J. rhombifolia subsp. delasotae. C–D. SEM micrographs illustrating the absence of stomata on the adaxial surface (C) and their presence on the abaxial surface (D) (arrows). F. Light micrograph of transverse section showing dorsiventral mesophyll and stomata on the abaxial epidermis (arrows). Scale bars:A: 250 μm; B–D: 50 μm; E–F: 100 μm. References: ade: adaxial epidermis; abe: abaxial epidermis; pm: palisade mesophyll; sm: spongy mesophyll; vb: vascular bundle.

FIGURE 3. Complete distribution of both subspecies of Jodina rhombifolia