Cladistic and Biogeographic Analyses of the Genera Moscharia and Polyachyrus (Asteraceae, Mutisieae)

The genera Moscharia (two species) and Polyachyrus (seven species) form a monophyletic group within tribe Mutisieae, subtribe Nassauviinae, defined by the leaves with auricles at their bases, and the capitula with 1-seriate involucre. A cladistic analysis of the species of the two genera was carried out using 22 characters from life cycle, external morphology, pollen, and trichomes. Polarity of the characters was based on the outgroup comparison method. One cladogram was produced, with 37 steps, a consistency index of 0.73, and a retention index of 0.75. The cladogram defines six monophyletic groups: (((Polyachyrus annus, (P. carduoides, (P. cinereus, (P. fuscus, P. gayi))), P. sphaerocephalus), P. poeppigii), (Moscharia solbrigii, M. pinnatifida)). The probable ancestral geographic area for the group, determined by Bremer9s method, is NorthCentral Chile area (308–358 south latitude). The study suggests that the Pleistocene could be the period of evolution of the ancestor of Moscharia and Polyachyrus. The genera Moscharia Ruiz et Pav. and Polyachyrus Lag. are found in Chile and Peru, occupying mainly dry habitats. Moscharia, with two species, was reviewed by Crisci (1974a) and Polyachyrus, with seven species and two varieties, was reviewed by Ricardi and Weldt (1974). Moscharia and Polyachyrus belong to subtribe Nassauviinae of Mutisieae, a phylogenetically basal tribe of Asteraceae (Bremer and Jansen 1992). These genera, together with species of Nassauvia and Triptilion, represent a morphologically distinctive group because the aggregation of their capitula into secondary inflorescences or pseudocephalia (Troll 1928; Leppik 1960; Weberling 1992), which are hypothesized to be an advanced evolutionary feature when compared to a regular capitulum. Stebbins (1967) has suggested that the union of few-flowered capitula into pseudocephalia would be a more efficient mechanism to increase the size of the functional inflorescence than the acquisition of new flowers into a reduced capitulum. There are three steps in the formation of pseudocephalia: (1) the capitula aggregate closely without losing their individual identities; (2) the capitula aggregate into a functional head, the individual capitula being still recognizable and without the formation of a pseudoinvolucre; and (3) obliteration of the identity of the individual capitula and acquisition of a pseudoinvolucre. Polyachyrus and Moscharia would represent the second and the third stages of this sequence, respectively (Crisci 1974a). Polyachyrus (Fig. 1A–B) is characterized by its monomorphic and espiciform pseudocephalia: all the capitula of the pseudocephalium have the same morphology, i.e., they are 2-flowered with an involucre of five bracts, and the main axis of the pseudocephalium is relatively long with the capitula sessile and spirally disposed on this axis. Moscharia (Fig. 1C–F), on the other hand, is characterized by its dimorphic and capituliform pseudocephalia: there is a central 1–2flowered capitulum with an involucre of 4–7 bracts, that is surrounded by 2-flowered capitula with an involucre of two bracts; the main axis of the pseudocephalium is shortened to form a head-like or capituliform structure. In both genera the pseudocephalium has a common involucre or pseudoinvolucre, which is more developed in Moscharia. Each capitulum in Moscharia and Polyachyrus consists of: a) one inner flower, the flower of the capitulum that is closest to the center of the pseudocephalium; b) one outer flower, the flower of the capitulum that is farthest from the center of the pseudocephalium; c) one pale, the bract situated between the two flowers of the capitulum; and d) one keeled bract, the outermost involucral bract in the capitula that surrounds one or all the flowers of the capitulum. The keeled bract can be convex and humped (Polyachyrus) or conduplicate and humped (Moscharia). There are three other bracts that surround the inner flower in the capitula of Polyachyrus. With regard to the other genera of Nassauviinae, Moscharia and Polyachyrus are closely related by homologies in their pseudocephalia (Crisci 1974a; Freire et al. 1993). Other authors (e.g., Hellwig 1985) reject the occurrence of pseudocephalia in Moscharia 34 [Volume 25 SYSTEMATIC BOTANY FIG. 1. Pseudocephalia and capitula in Polyachyrus and Moscharia. A–B, Polyachyrus foliosus; A, pseudocephalium espiciform without a developed pseudoinvolucre; B, capitulum. C–D, Moscharia solbrigii; C, pseudocephalium capituliform with a developed pseudoinvolucre; D, capitulum. E–F, M. pinnatifida; E, pseudocephalium with a developed pseudoinvolucre; F, capitulum. (Modified from Crisci 1974a). if 5 inner flower; kb 5 keeled bract; of 5 outer flower; pa 5 pale; ps 5 pseudoinvolucre. 2000] 35 KATINAS & CRISCI: MOSCHARIA AND POLYACHYRUS and suggest a close relationship between Moscharia and Leucheria, another member of Nassauviinae on the basis of head development and chromosome number. In a cladistic analysis of Nassauviinae (Katinas 1994), however, Leucheria is not closely related to the Moscharia-Polyachyrus group. According to Crisci (1974a) when we compare the pseudocephalium of Polyachyrus with the floral head of Moscharia the real homology of the latter is easy to ascertain. Each group of two flowers and their surrounding bract in the head of Moscharia is equivalent to a primary head in the pseudocephalium of Polyachyrus, the difference being that the bracts have been reduced from five to two. The central group of one to two flowers and their surrounding bracts correspond to a much reduced first-order head; these bracts are comparable with the accesory bracts of the capitulum of Polyachyrus. Finally, the geographic distribution of both genera is of interest. Polyachyrus is distributed in the Andean and coastal dry areas of Chile and Perú, from 88 to 358 south latitude in South America, and the genus Moscharia is endemic to most of the area recognized as Central Chile, from 298 to 358 south latitude. These areas of Chile and Perú are of biogeographic interest because of their high endemism (Rundel et al. 1991; Morrone et al. 1997) and the competing hypotheses that have attempted to explain distributions of taxa in this restricted area (e.g., Kalin Arroyo et al. 1982; Solervicens A. 1987; Rundel et al. 1991; Morrone et al. 1997). The objectives of this paper are: (1) to present results of a cladistic analysis of the species of Moscharia and Polyachyrus; (2) to analyze the character evolution of leaves, involucre and flowers, and pappus; and (3) to estimate the probable location of an ancestral geographic area for Moscharia and Polyachyrus. MATERIALS AND METHODS Cladistic Analysis. TAXA. The species of Moscharia and Polyachyrus, considered here as terminal taxa, form a monophyletic group that is distinguished from other related genera by the leaves with basal auricles, and capitula with 1-seriate involucre (Freire et al. 1993) (Fig. 2). Data for the morphology of the species of Moscharia and Polyachyrus were taken from previous studies (Crisci 1974a; Ricardi and Weldt 1974) and from the analysis of herbarium specimens. Table 1 lists these species, their acronyms, geographical distribution, and specimens analyzed with vouchers. Nomenclature for Moscharia, Polyachyrus, and related genera follows Crisci (1974a, b) and Ricardi and Weldt (1974). OUTGROUP SELECTION. The apomorphic character state was identified by the outgroup comparison method (Watrous and Wheeler 1981). The phylogenetic hypothesis proposed for the subtribe Nassauviinae (Crisci 1980; Freire et al. 1993) provides a basis for choosing an appropiate outgroup for cladistic analysis of Moscharia and Polyachyrus (Fig. 2). This hypothesis recognizes the group formed by Cephalopappus Nees et Mart., Moscharia, Polyachyrus, Triptilion Ruiz et Pav., and Nassauvia Lag. (including Calopappus Meyen) supported by the reduced capitula. Moscharia, Polyachyrus, Triptilion, and Nassauvia form a monophyletic group based on the pappus shorter than the corolla, chaffy pappus, and the pollen grains with a tectum and infratectum of the same thickeness. Triptilion and Nassauvia form a monophyletic group suggested by the deciduous pappus, 2–6 pappus bristles, colpi membranae with sexine processes, spheroidal to spheroidal-oblate pollen, strengthened testa epidermis, and single 2celled cypsela hairs. The Triptilion–Nassauvia group is sister to Moscharia and Polyachyrus, therefore this group has been used as the outgroup of Moscharia and Polyachyrus. The outgroup was abbreviated OUT for the analysis. CHARACTERS. Data from 22 characters (Table 2) were derived from the life cycle, leaf morphology, pseudoinvolucre morphology, capitula arrangement and morphology, corolla surface and morphology, pollen, cypsela vestiture, and pappus morphology. Multistate characters (2, 6, 13, 20, and 22) were treated as unordered (5 non additive). Characters 6, 8, 15, and 16 are inapplicable characters in the outgroup (since they are related to traits absent in it), they were coded as ’’? ’’ in the data matrix and treated as missing data during the analysis. Character 1 was variable in the outgroup and therefore it was treated as polymorphic during the analysis and coded in the data matrix as ‘‘a’’. Table 3 contains the data matrix, which was analyzed with the Wagner maximum parsimony algorithm of PAUP* version 4.0 (Swofford 1999) using the ‘‘branch and bound’’ option (equivalent to ie* option of Hennig86; Farris 1988). The bootstrap method (Felsenstein 1985) and Bremer support (Bremer 1988; Donoghue et al. 1992) were employed to evaluate the reliability of the phylogenetic estimates. One hundred replicates were performed in the bootstrap method. The program MacClade version 3.0 (Maddison and Maddison 1992) was used for examination of character distribution. 36 [Volume 25 SYSTEMATIC BOTANY FIG. 2. Outgroup hypothesis for Moscharia (MOS) and Polyachyrus (POL), simplified from cladograms of Crisci (1980) and Freire et al. (1993). Nassauvia 5 NAS, Cephalopappus 5 CEP, and Triptilion 5 TRI. Historical Biogeography AREAS OF ENDEMISM. Delimitation of areas of endemism have been discussed by several authors (Humphries and Parenti 1986; Harold and Mooi 1994; Morrone 1994). An area of endemism is usually defined as a geographic region to which one or more taxa are confined. In this study, areas are circumscribed so they comprise several endemic taxa, following the studies of Cabrera and Willink (1980) and Morrone et al. (1997). The areas considered in this study are (Fig. 3): 1. Coastal Desert ranges throughout the Peruvian and Chilean coast from 58 to 308 S latitude. It is a dry area dominated by annual herbs, xerophitic shrubs and cacti. This area is characterized by a high percentage of endemic taxa (Rundel et al. 1991), e.g., Balbisia peduncularis (Geraniaceae), Domeykoa (Apiaceae), Eulychnia breviflora (Cactaceae), Leucocoryne narcissoides (Amarilidaceae), Neoporteria chilensis (Cactaceae), Oxyphyllum, Polyachyrus annus, and P. cinereus (Asteraceae). 2. Cardonal covers the west facing slopes of the Andes of Peru and Chile, approximately between 1500 m and 3000 m from 58 to 308 S latitude. It is a narrow belt of open desert scrub dotted with cacti that become the dominant life form in the north. Some endemic taxa are Ambrosia fruticosa, Diplostephium tacorense, Mutisia acuminata var. bicolor, M. hastata, M. arequipensis, M. mathewsii, and Polyachyrus sphaerocephalus (Asteraceae). 3. North Central Chile ranges from 308 to 358 south latitude in Chile. This is a dry area characterized by the high percentage of endemic taxa, such as Chaetanthera glandulosa (Asteraceae), Echemoides chilensis (Araneae, Gnaphosidae), Hyperoides murinus, Listroderes hoffmani (Coleoptera, Curculion2000] 37 KATINAS & CRISCI: MOSCHARIA AND POLYACHYRUS TABLE 1. Taxa studied, acronyms, geographical distribution, and specimens examined with vouchers (herbarium acronyms from Holmgren et al. 1990). Taxa Acronym Geographical distribution Specimens examined