Systematics of Paranephelius Poepp. & Endl. (Liabeae-Asteraceae):

A case study in high-elevational speciation.

 

 

Michael O. Dillon

Department of Botany

The Field Museum

Chicago, IL 60605, USA

 

Mario Zapata Cruz

Museo de Historia Natural

Universidad Antenor Orrego

Trujillo, Peru

 

 

Introduction

 

Diversity in the Asteraceae is especially rich within the Andes of South America (Funk et al. 1995) and many genera are restricted to specific high-elevation habitats, such as, páramo, jalca,  and puna.  Several tribes have genera that have radiated into these specialized habitats, e.g., Oritrophium and Plagiocheilus (Astereae); Jalcophila, Loricaria, and Mniodes (Gnaphalieae), Aphanactis (Heliantheae); Perezia (Mutisieae); Hypochaeris (Lactuceae); and Werneria and Xenophyllum (Senecioneae).  The Liabeae, with 15 genera and perhaps 180 species, is the only tribe with an entirely neotropical distribution and northern Peru is a center of both generic and species diversity (Funk et al. 1996).

 

 Within the Liabeae, Paranephelius contains seven species occupying habitats between 3000-4000 m, from Peru through Bolivia and into northwestern Argentina.  While a couple of species are recorded from as low as 2200 m, Paranephelius is most diverse above 3000 m and can reach 4600 m.  In Peru, four species are found in alpine sites, from wet jalca or páramo formations in the north to the drier puna of central and southern Peru. Two species have distributions extending from southern Peru into high-elevation, altiplano of Bolivia, and one species is known only from Bolivia and northwestern Argentina (Fig. 1).

 

Paranephelius is composed of acaulescent herbs with showy, yellow capitula, sessile in the center of a basal rosette of leaves, often with bullate leaf surfaces (Fig. 2).  The genus has several synapaorphies within the tribe Liabeae (Funk et al. 1996, Fig. 3), including sessile rosette habit, ray florets with tomentum on the outer surfaces, sessile capitulescences, and large achenes.  Robinson (1983) related it to Pseudonoseris H. Rob. & Brett., a genus of three species restricted to Peru; and established the subtribe Paranepheliinae H. Rob. with these two genera.

 

Research Plan

 

            Paranephelius represents an interesting example of specific radiation throughout a range of high-elevations habitats over a large latitudinal range, 3°-25°S, but with greatest diversity in northern Peru where no fewer than five species are recorded.  With the exception of the excellent generic treatment by Robinson (1983) the genus has not had a taxonomic or monographic treatment at the level of species, and a key to species has yet to be published.   We propose to study the Paranephelius of Peru, to include collecting throughout the range of the genus in Peru where the highest species diversity is recorded.  The resulting monograph will provide detailed species descriptions, morphological cladistic analysis, and examine biogeography, character evolution, and species boundaries in relation to the putative phylogeny. 

 

            Workers have commented that the species should perhaps be reduced. Cabera (1978, p. 467) discussed the possibility that Paranephelius asperifolius (as Liabum) may be conspecific with P. uniflorus. Further, the specific boundaries between P. jelskii and P. ferreyrii will be examined to determine isolating mechanisms.  Paranephelius ovatus is by far the most wide-ranging and morphologically variable species in the genus, and that species will be examined for patterns of variability in relationship to geography and habitat preference throughout its range.  The greatest concentration of species is to be found in the northern Peruvian department of Cajamarca.  This small department (~30,000 km2) has no fewer than four Paranephalius species recorded, and in that department, a close examination of patterns of sympatry and potential isolating mechanisms will be accomplished.  

 

             In our attempt to develop and test hypotheses of evolutionary relationships in Paranephelius, we will also examine the putative sister taxon, Pseudonoseris.   As logical outgroups in our cladistic analysis, Pseudonoseris striata and P. szyszylowiczii, both which occur in northern Peru, will be collected and added to the analysis. This will also allow us to test the strength of the subtribe Parnepheliinae in relation to the rest of the tribe Liabeae. 

 

            In connection with an ongoing floristic inventory of the jalca flora of northern Peru, we have collected several Parnephelius species and silica dried leaf material suitable for DNA analysis. It is our hope that a molecular systematics component can be added to the current investigation in an attempt to develop a more robust phylogeny for defining species relationships, testing biogeographic hypotheses, and examining character evolution in this monophyletic group.

 

Generic Description

 

Paranephelius Poepp. & Endl., Nov. Gen. et Sp., 3: 42, pl. 248, 1843. [Type-species: Paranephelius uniflorus Poepp. & Endl.]

 

            Perennial, acaulescent or short-stemmed herbs, with milky sap. Leaves in basal rosette, sessile, the blades ovate to lanceolate, the lower surfaces tomentose, the upper surfaces rugose-bullate, marginally frequently lobed.  Capitulescences of solitary capitula, or 2-3 and then sessile in basal leaf rosettes.  Capitula heterogamous and radiate, sessile; involucres broadly campanulate, the phyllaries ca. 4-seriate. Ray florets 20-35; corollas ligulate, yellow, tomentose.  Disc florets 2-35; corollas yellow.  Cypselas ca. 10-ribbed, glabrous or pubescent; pappus 2-seriate, the outer of short flattened bristles or scales, the inner of longer scabrid bristles.

 

Species List and Distribution

 

1. Paranephelius asperifolius (Musch.) H. Rob. & Brettell [Bolivia, Argentina] – Fig. 4.

2. Paranephelius bullatus A.Gray ex Wedd. [Peru: Huánaco]

3. Paranephelius ferreyrii H.Rob. [Peru: Cajamarca, La Libertad]

4. Paranephelius jelskii (Hieron.) H.Rob. & Brettell [Peru: Cajamarca]

5. Paranephelius ovatus Wedd. [Peru: Ancash, Apurimac, Ayacucho, Cajamarca, Cusco, Junin, Lima, Puno] – Fig. 2.

6. Paranephelius uniflorus Poepp. & Endl. [Bolivia, Peru: Cajamarca, Cusco, Junin, Huáncavelica, Pasco] – Fig. 5.

7. Paranephelius wurdackii H.Rob. [Peru: Amazonas, Cajamarca]

 

 

Literature

 

Cabrera, A. L.  1978. Flora de la Provincia de Jujuy. 10: 1-726. Colección Cientifica de INTA; Buenos Aires, Argentina.

Funk, V. A., H. Robinson, M. O. Dillon. 1996. Liabeae: Taxonomy, phylogeny and biogeography. In D.J.N. Hind & J.J. Beentje (eds.).  Compositae: Systematics. Proceedings of the International Compositae Conference, Kew, 1994. Vol. 1. pp. 545-567. Royal Botanic Garden, Kew.

Funk, V. A., H. Robinson, G. S. McKee, & J. F. Pruski. 1995. Neotropical montane Compositae with an emphasis on the Andes.  In S. Churchill et al. (eds.). Biodiversity and conservation of Neotropical Montane Forests, pp. 451-471. New York Botanical Garden, New York.

Robinson, H. 1983. A generic review of the tribe Liabeae (Asteraceae). Smithson. Contr. Bot. 54: 1-69.

 

 

Fig. 1. Distribution of Paranephelius

 

 

 

Fig. 2. Paranephelius ovatus Wedd.

 

 

Fig. 3. Liabeae Cladogram (Funk et al. 1996).

 

Fig. 4. Paranephelius asperifolius (Musch.) H.Rob. & Brettel

(Cabrera, 1978, p. 466)

 

Fig. 5. Paranephelius uniflorus Poepp. & Endl.

(Robinson, 1983, p. 46)