Beneficios en la utilización de las TIC’s

Chaetanthera species are monoecious. The ray florets are functionally female, with greatly reduced sterile anthers (inconspicuous staminodes). They are radiate bilabiate and zygomorphic (after KATINAS et al. 2008), with a shortly 3-dentate ligule and a bifid inner lip,

arranged in a single series, and yellow (e.g., C. linearis, C. glabrata) or white (C. albiflora, C. philippii). C. ciliata has been observed as having a cerise form (Hershkovitz, pers. comm.; F. Lira photostream 11.06.2008) and C. microphylla usually has brick-red rays. Species such as C. serrata and C. philippii have distinct pink to red dorsal stripes on the exerted ray ligules. With the exception of C. perpusilla and C. ramosissima, the ray florets are conspicuously exerted beyond the involucrum. The disk florets are non-radiate, bilabiate and slightly zygomorphic. They are always yellow. The typical form of disk and ray florets is illustrated in Fig. 11 (E, F).

Oriastrum species may be monoecious or gynodioecious. The pistillate ray florets from bisexual capitula (Fig. 11A) are radiate bilabiate and zygomorphic, and have irregularly formed 3-dentate ligules, and a bifid inner lip. They are usually cream-coloured or white, often flushed with pink. O. abbreviatum has yellow rays and some herbarium sheets report yellow rays for O. cochlearifolium. The disk florets are are non-radiate bilabiate and slightly zygomorphic. They are always yellow, and bisexual with fertile anthers (Fig. 11B). Gynodioecious species are found only in a closely related group of species in Oriastrum subgenus Egania and include O. dioicum, O. polymallum, O. pulvinatum, O. revolutum and O. stuebelii. Some individuals in these species have capitula entirely composed of pistillate ray florets, which are somewhat dimorphic (see Fig. 11C, D).

Figure 11: Floret variation. Ray and disk florets from the gynodioecious O. dioicum (A - D), and the monoecious C. kalinae (E - F). A. Ray floret from bisexual capitula. B. Disk floret from bisexual capitula. C & D. Dimorphic ray florets from female capitula. E. Ray floret from bisexual capitula. F. Disk floret from bisexual capitula. Scale bar = 2 mm.

III Variation of characters in Chaetanthera & Oriastrum 37

The comparative length of the ray floret ligule (short or long) has been used as a character defining the difference between Chaetanthera and Oriastrum species in previous publications (CABRERA, 1937; TELLERÍA & KATINAS, 2004). While it certainly holds true that the ray florets of Oriastrum species (3.0 – 13.0 mm) are often shorter than those of many Chaetanthera species (4.0 – 26.0 mm), more than half the Chaetanthera species have ray florets whose mean length lies within the normal range of Oriastrum ray floret lengths.

Measurements were made of the ray floret length, ray floret tube length, ray ligule width, disk floret length and disk floret tube length for all species as part of the species descriptions. When mean ray length (RL) is plotted against mean disk length (DL) (see Fig. 12, data in Table 21a, Appendix 1) the same relationship is seen between the disk and ray florets for both Chaetanthera and Oriastrum species. C. taltalensis has smaller florets overall but have the same ray length to disk length proportion as C. kalinae, and the trend is continued in C. villosa, even though the rays of C. villosa (24.0 mm) are six times longer than those of C. taltalensis (3.8 mm). In Oriastrum, O. famatinae (RL = 4.4 mm) and O. acerosum (RL = 8.0 mm) have the same ray length to disk length proportion, despite the difference in size. There are exceptions to this relationship in both genera. For example, C. elegans has longer rays than expected. O. polymallum has distinctly shorter ray florets while O. werdermannii has longer ray florets than expected.

Figure 12: Ray floret length (RL) and disk floret length (DL) variation. Graph plotting RL against DL for Oriastrum (black shapes) and Chaetanthera (red shapes) for lowland (<1500 m) [▲] and upland (>1800 m) [●] species.

The ray and disk floret variation was analyzed in the context of the altitude zones in which the species are generally found. An index of ray floret length to disk floret length (RL:DL) was generated. The means of the RL:DL indices for the species in each altitude zone were tested using Students paired T-test assuming a two-tailed distribution for equal variance (homoscedastic t-Test). Tests for significance within Oriastrum, over 2 altitude zones (Andino – Altoandino 2700 – 3500 m; Andino superior > 3500 m) showed no significant differences in the floret proportions (p = 0.29). Only a weak significance was detected between the Mediterranean-matorral and Andean species within Chaetanthera (p < 0.01). However, when all the species in both genera were attributed either to a lowland Mediterranean-matorral zone (<1500 m.a.s.l.) or an upland Andean zone (>1800 m.a.s.l.), there was a significant difference (Students T-test, p < 0.0001) between the RL:DL ratios. I conclude that the lowland species have more showy capitula i.e., tend to have longer ray florets in relation to the disk florets (n = 15, RL:DL = 1.75 ± 0.09) than the upland species (n=31, RL:DL = 1.39 ± 0.04). This renders the use of ray floret ligule measurements as a generic identifier redundant.

Within the lowland species the following had extreme ray:disk ratios: C. elegans (2.3), C. microphylla (1.2) and O. werdermannii (2.3). Within the Andean species the following had extreme ray:disk ratios: C. renifolia (1.7), C. peruviana (1.7) and O. polymallum (0.6). All these species also show peculiarities in aspects such as locality, breeding system and other morphological and anatomical features. Although there are some disjunctions of size between selected taxa, in the majority of species of Oriastrum and Chaetanthera, ray floret length and disk floret length reflect the overall aspect of the capitula, while the ratio between them appears, to be a function of altitude. The possible correlates between altitude zone, habitat and breeding system are not discussed here.