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

Diagnosis.

Trees or shrubs, lower leaflet surfaces tomentose; apices emarginate; fruits with variable numbers and placements of flattened, almost cylindrical or long spines, densely lanose, tomentose or villous.

Type.

Polylepis reticulata Hieron.

Notes.

The sectional epithet Reticulatae is a plural adjective agreeing in gender with Polylepis . Section Polylepis Reticulatae , first informally recognized by Simpson (1979) and later recovered as monophyletic in the phylogenetic analysis of Schmidt-Lebuhn et al. (2006a), contains species with relatively few lateral leaflets pairs, rugose or shiny upper leaflet surfaces, emarginate leaflet apices and felt-like covering on the lower leaflet surfaces. All species placed in this section have the lower leaflet surfaces with an evenly distributed dense layer of short, white to yellowish pannose hairs, admixed with short to moderately long tomentose hairs. As in section Polylepis Sericeae , species in this section have fruits with straight or recurved spines. Polylepis microphylla , P. occidentalis and P. quadrijuga have many lateral leaflet pairs (3-6), but all three have rugose or shiny upper leaflet surfaces and emarginate leaflet apices. The most distinct species of this section is P. hieronymi , which has sparsely tomentose upper leaflet surfaces and almost cylindrical fruits with long spines. This is also the geographically most remote species, being separated by over 1500 km from the other members of the section. Polylepis microphylla also has atypical, turbinate fruits. Polylepis quadrijuga is similar in some ways to P. frontinensis and P. lanuginosa of section Polylepis Sericeae , but these species do not have the dense layer of short pannose hairs admixed with tomentose hairs on the lower leaflet surfaces. Table 5 provides an overview of the arrangement of the taxa by different authors.

Climatic niches in Polylepis sect. Reticulatae

Many species of this section differ notably in the Mean Annual Temperature (MAT) of their climatic niches, with only P. quadrijuga and P. simpsoniae not being statistically different (Fig. 46 ). Polylepis hieronymi grows under the highest temperatures (mean of 12.3 °C MAT), followed by P. occidentalis (10.7 °C), whereas P. reticulata (6.4 °C) and P. weberbaueri (5.2 °C) grow under the coldest conditions. These differences of up to 7 °C correspond to elevational differences of well over 1000 m. Regarding Mean Annual Precipitation (MAP), most of the species in this group grow under relatively arid conditions with similar averages of precipitation (807-835 mm MAP). Species growing in even drier areas are P. microphylla (675 mm MAP) and P. weberbaueri (731 mm), whereas those growing in most humid conditions are P. reticulata (1021 mm) and P. quadrijuga (1638 mm). Most species are allopatric, but in Ecuador, P. reticulata and P. simpsoniae co-occur close to each other and have distinct climatic niches, with P. reticulata growing under colder and more humid and P. simpsoniae under warmer and drier conditions.

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