Polylepis section Incanaee T.Boza & M.Kessler, 2022

Boza Espinoza, Tatiana Erika & Kessler, Michael, 2022, A monograph of the genus Polylepis (Rosaceae), PhytoKeys 203, pp. 1-274 : 1

Polylepis section Incanaee T.Boza & M.Kessler sect. nov.

Diagnosis.

Trees or shrubs; lower leaflet surfaces glabrous or with hispid, puberulous, lanate, tomentose, or villous hairs; fruits with irregular flattened ridges with a series of spines, glabrous to densely hispid, tomentose or villous.

Type.

Polylepis incana Kunth.

Notes.

The sectional epithet Incanaee is a plural adjective agreeing in gender with Polylepis . Section Polylepis Incanaee contains species with usually few lateral leaflet pairs (often only one), frequently glabrous upper leaflet surfaces, lower leaflet surfaces glabrous or with a dense layer of very short pannose hairs rarely mixed with tomentose hairs (as in P. besseri and P. incarum ) or mostly with tomentose, lanate or villous hairs. Furthermore, fruits in this section bear 2-5 irregular, hard, flattened ridges with a series of spines. Table 8 provides an overview of the arrangement of the taxa by different authors.

Within section Polylepis Incanaee , we recognized three subsections, based on their morphological distinctness as follows: subsection Polylepis Racemosae Racemosae (9 species) with lanate, tomentose or villous lower leaflet surfaces, 2-4 lateral leaflet pairs and fruits densely covered by tomentose or villous hairs; subsection Polylepis Besseria Besseria (5 species) with short pannose or tomentose lower leaflet surfaces, 1-2 lateral leaflet pairs and fruits with 2-5 flattened ridges with a series of spines; and subsection Polylepis Incanaee Incanaee (6 species) with pannose lower leaflet surfaces, one lateral leaflet pair and densely villous fruits. Within each subsection, species are essentially allopatric in distribution.

Climatic niches in Polylepis sect. Incanaee

Climatic niches among the species of this group differ notably (Figs 74 - 76 ). Polylepis tarapacana grows under the coldest conditions (mean of 2.6 °C Mean Annual Temperature, MAT); whereas other species, such P. crista-galli (11.2 °C), P. incanoides (11.0 °C), P. besseri (10.8 °C) and P. nana (10.4 °C), grow under noticeably higher temperatures. These differences of up to 7.6 °C correspond to about 1400 m elevation. Regarding Mean Annual Precipitation (MAP), P. lanata grows under the most humid conditions (mean of 1547 mm MAP), followed by P. triacontandra (1057 mm). In contrast, species growing in drier areas are P. tarapacana (180 mm MAP), P. rugulosa (210 mm) and P. tomentella (412 mm).

Focussing on the individual subsections, the five species of subsect. Polylepis Besseria Besseria are allopatric and mostly have rather similar climatic niches, although most species have some level of climatic differentiation; only P. besseri and P. crista-galli are identical. Subsection Polylepis Racemosae Racemosae includes seven allopatric species that again mostly differ in either MAP or MAT, partly quite considerably. For example, Polylepis lanata and P. triacontandra occur close to each other in Bolivia, but have ecological differences, with P. triacontandra growing under relatively colder and more humid conditions. Additionally, P. lanata and P. sacra , long thought to be the same species ( Simpson 1979; Mendoza and Cano 2012), have distinct climatic niches, with P. lanata growing under much warmer and humid conditions than P. sacra . Within this subsection, only P. acomayensis and P. pacensis have identical climatic niches. Finally, in subsect. Polylepis Incanaee Incanaee , all species are climatically distinct. For instance, Polylepis incanoides , P. nana and P. tomentella all occur in Bolivia, but P. tomentella grows under comparatively cold and dry conditions, P. incanoides under warm and humid ones and P. nana under warm and dry ones.

Figures

Figure 12. Box plots showing the climatic niches of the species of the subsections Lanuginosae, Pauta and Pepea in relation to Mean Annual Temperature (MAT) (A) and Mean Annual Precipitation (MAP) (B). The ends of each box represent the upper and lower quartiles and the median is indicated with a bold line inside the box; the whisker lines extend to the highest and lowest observations, except when observations are higher or lower than the interquartile range (i. e. outliers), in which case they are indicated by a dot. Box plots that share the same lowercase letters within each subsection are not significantly different at p = 0.05. Vertical lines represent subsectional divisions.

Figure 74. Box plots showing the climatic niches of the species of subsection Polylepis Racemosae Racemosae in relation to MAT (A) and MAP (B). See Fig. 12 for details on data presentation.

Figure 76. Box plots showing the climatic niches of the species of subsection Polylepis Incanaee Incanaee in relation to MAT (A) and MAP (B). See Fig. 12 for details on data presentation.