**2. Population biology**

#### **2.1 Geographic distribution**

Seven morphological distinct taxa of the *Magnolia pacifica* species complex occur in western Mexico (**Figure 1**), however most comparisons in this study include the three species growing along a continentality and moisture gradient, from west to east: *M. vallartensis*, *M. pacifica* and *M*. *pugana* and only few comparisons (morphological and genetical) also include discussion of the *M*. *granbarrancae* and *M*. *talpana* here described as new.

#### **2.2 Morphological differentiation and adaptations**

#### *2.2.1 Habit and foliage*

All species in the *Magnolia pacifica* complex are evergreen long leaved and usually sympodial and tortuous trees. *M. vallartensis* and the new *M*. *granbarrancae* are generally small trees (8.0–15.0(23.0) m) with smaller trunk diameter at breast height (1.3 m) (0.2–0.5 m), while *M*. *pugana*, *M. pacifica* and the new *M. talpana*

are large trees (15.0–35.0 m) with thicker trunks, (0.3–1.6 m) in diameter at breast height.

The leaves in *Magnolia vallartensis* are distinctively broadly elliptic to elliptic or occasionally oblong, while the other four species are narrowly elliptical to elliptical to oblanceolate. The width to length ratio of mature leaves is larger in *M*. *vallartensis* (45–51%) than that of the other species *M. pacifica* (30–39%).

#### *2.2.2 Flowers and floral visitors*

Flowers of *Magnolias* in western Mexico differ in their pollination chamber*,* whether having a fully distinct chamber at female phase (day zero) involving all petals, like in *M*. *vallartensis*, *M*. *talpana* and *M*. *iltisiana,* or with an incipient or loose chamber involving mostly the inner petals. *M*. *vallartensis*, has a distinct subglobose pollination chamber, *M. iltisiana* has an oblongoid one and *M*. *talpana* has the narrowest oblongoid and tight chamber. *Magnolia granbarrancae* and *M*. *pugana* have the greater width to length ratio on petals and sepals while *M. talpana* has the smallest one.

Like other basal angiosperm lineages such as Araceae, Arecaceae, Cyclanthaceae, Nymphaeaceae and Annonaceae, the family Magnoliaceae exhibits floral traits that have been hypothesized as evolutionary adaptations to beetle pollination (cantharophily) [21]. In general, large, bisexual flowers, with petals, tepals or floral receptacles forming a bowl shape, have been considered as distinctive features of the beetle pollination syndrome [22]. Within the Magnoliaceae, specific traits include the development of female floral structures before the male ones (protogyny) to ensure cross pollination, floral odors, floral movements and the production of heat by reproductive structures as a result of biochemical reactions (thermogenesis) [23].

Coleoptera (Scarabaeidae) have been observed feeding and mating in flowers of *Magnolia pugana* and *M. pacifica* (*M. talpana*), causing damage to the petals and sepals (**Figure 2**). Despite cantharophily is the most common pollination syndrome in basal angiosperms, hymenopterans have been observed visiting flowers of *M. pacifica* s. s. (Huajicori group) and *M*. *vallartensis*. In the latter species we can confirm that hymenopterans play a role in pollination given that we were able to photograph some bees with significant amounts of pollen attached to the specialized hairs in their hind legs (**Figure 2**). The known floral visitors to each of the studied *Magnolia* species are listed in **Table 1**. Insect pollination represents a fundamental ecosystem service in natural habitats, particularly for obligate insect-pollinated plant species [26, 27], however, there is still little knowledge on insect floral visitors and the floral biology of most of *Magnolia* species, therefore, further studies including more field observations are much needed.

#### *2.2.3 Fruits and seeds*

The fruits of *Magnolia,* often called polyfollicles, consist of spirally arranged carpels, initially free and in some species becoming concrescent. Dehiscence in all three species of the *M. pacifica* complex is dorsal and bivalve. *Magnolia granbarrancae* and the Huajicori group have ovoid and smaller fruits (**Figure 3**). Basal carpels are larger in *M. pacifica* than in any other species, while the carpel apex are distinctively more pronounced in *M*. *vallartensis*.

*Magnolia* seeds are attached to the fruit by thin funicular threads that keep them suspended after release for one or two days before falling to the ground. They have a three-layer coat, the outer one called sarcotesta is bright, red to orange colored (that is attractive for their dispersers, the birds), fleshy and with persistent odor oils *How to Save Endangered Magnolias? From Population Biology to Conservation Action… DOI: http://dx.doi.org/10.5772/intechopen.94346*

#### **Figure 2.**

*Known floral visitors to the magnolias in the* Magnolia pacifica *species complex. A–C,* Strigoderma sulcipennis *on* M. pugana*; damage to the petals and sepals by the beetle is visible. D–F,* Cyclocephala *sp. sheltering inside flowers of* M. talpana*. G–I, representatives of* Frieseomelitta nigra *visiting stamens of* M. vallartensis*; pollen can be seen attached to their hind legs. Photographs A–C by G. Hernández-Vera, D–I by M. Muñiz-Castro.*


#### **Table 1.**

*Known insect floral visitors to each of the studied* Magnolia *species. The "x" indicates unidentified taxonomic rank.*

that make it impervious to water and gas exchange, containing inhibitors for germination and can protect it from some diseases and predators; the middle cover is called testa and provides mechanical protection as it is hard and bony, with a dark or light-colored depending on the species; the inner coat is a thin membrane that

surrounds the endosperm, within which a rudimentary embryo is present [28, 29]. For the magnolias of the pacific complex, the seeds are prismatic to triangular with scarlet red sarcotesta and light-colored testa, presenting more similarity between *M. pugana* and *M. vallartensis* with seeds of the same size (9–12 � 7–8 mm) and shape (sub-cylindrical or round-compressed) and small variations with *M. pacifica* seeds, that are slightly bigger (8–14 � 7–11 mm) and sub-cylindrical to cylindrical or rounded to compressed [13].
