**Abstract**

Numerous Neotropical *Magnolia* species are endangered and red-listed by the IUCN. Here we highlight major results from over a decade of research on endangered magnolias in western Mexico. Particularly, we compare three species of *Magnolia* (*M*. *pugana*, *M. pacifica* and *M*. *vallartensis*) along a large-scale continentality and moisture gradients, in terms of a) their morphological adaptations, b) genetic structure, diversity, and differentiation, c) reproductive phenology, and d) floral scents and their floral visitors. Fieldwork along this gradient unveiled two new species of *Magnolia* sect*. Magnolia; M. granbarrancae* and *M. talpana*. We found that most continental populations have a higher extinction risk than those with greater maritime influence, due to their lower genetic diversity, and greater fragmentation, isolation, and water stress. Also, these populations are more vulnerable to the environmental conditions predicted with the global warming climate scenarios. We share fieldwork experience and advise on pre-germination treatments and seed dormancy. We propose an ex-situ and in-situ conservation strategy, identify new challenges, and suggest future directions of collaborative work as a global *Magnolia* conservation consortium.

**Keywords:** allopatric radiation, conservation, floral scents, genetic diversity and differentiation, new species, species distribution modeling, pre-germination treatments

### **1. Introduction**

Magnolias have captivated mankind since ancient times, their lush evergreen foliage, varied floral scents and spectacular flowers make them highly attractive. Distributed from temperate to tropical areas of the Americas and Asia, they have an extraordinary value in horticulture, they are harvested from natural forests, either as a beauty item for solemn ceremonial rites or as a source of wood for construction, food, and traditional medicine [1, 2].

The family Magnoliaceae Juss. [3] belongs to one of the basal clades in the angiosperms, it consists of 350 species, two genera, *Liriodendron* L. [4] and *Magnolia* L. [4] and 15 sections [5]. It is disjunct and bicontinental; in the America and SE Asia, from near sea level to 3400 m [6].

The fossil record suggests a North American origin for the family, migrating east through the Disko Island, Greenland, and Thulean Landbridge, with a range expansion into Europe and eventually to Asia. The cooling of the climate during the mid-Cenozoic resulted in a migration to lower latitudes and the extinction of Magnoliaceae in Europe and Siberia. Finally, the Ice-house conditions of the late-Cenozoic drove the group further south to highlands of Central and South America, as well as the mountains in South-east Asia [7].

In Mexico, as a result of allopatric speciation, there are 36 species in three sections of *Magnolia*: *M*. section *Macrophyllae* Figlar & Noot. [8] with five species of dorsal dehiscence [1, 9], *M.* sect. *Talauma* (Juss.) Baill. [3, 10] with 13 species mostly of ventral dehiscence [2] and *M*. sect. *Magnolia* with 18 species of dorsal dehiscence [11, 12].

In western Mexico, there are eight species of *Magnolia* [13], two belong to *M*. sect. *Talauma*: *M. jaliscana* A. Vázquez & R. Guzmán [14] and *M. ofeliae* A. Vázquez & Cuevas [15]— both confined to the lower slopes of the Pacific Lowlands province at the edge of the Sierra Madre del Sur province— and six belong to *M*. sect. *Magnolia*: *M. iltisiana* A. Vázquez [11], from the highlands of the Sierra Madre del Sur; *M. pacifica* A. Vázquez [11] from the western end of the Sierra Madre del Sur province to the western end of the Transmexican Volcanic Belt province; *M. pugana* (Iltis & A. Vázquez) A. Vázquez & Carvajal [16] from the canyons and valleys north of Guadalajara city, in the Transmexican Volcanic Belt; *M. vallartensis* A. Vázquez & Muñiz-Castro [14] in the Pacific Lowland province southeast of Puerto Vallarta; and the two species here described as new (**Figure 1**).

Here, we mostly focus in the species which constitute the *Magnolia pacifica* species complex [11], consisting of species with glabrous ellipsoid fruits distributed from tropical climate lowlands to temperate climate mountains in the confluence of four biogeographic provinces Sierra Madre Occidental, Sierra Madre del Sur, Pacific Lowlands and Transmexican Volcanic Belt [17] (**Figure 1**). Populations of the Barrancae Group, occurring in the Río Verde region in the Zapotlanejo e Ixtlahuacán del Río municipalities (north of Guadalajara city) [18] are here described as a new species (*M*. *granbarrancae*). Similarly, populations from the mountains of southern Talpa de Allende in W Jalisco are here described as a new species: *M*. *talpana;* while several populations from northern Nayarit, considered morphologically distinct from *M. pacifica* sensu stricto are here designated as the Huajicori group.

Magnolias in western Mexico, occur in four of its six biogeographic provinces, isolated in canyons ("barrancas") or protected ravines of mountains, with minimum if any gene flow among their populations. They have undergone allopatric radiation, diverging in morphology, genetics, phenology, floral scents, and occupy different ecological niches (**Figure 1**) [11, 14, 18–20].

Here we aim to compare three species of *Magnolia* along a large-scale continentally and moisture gradients, in terms of (a) their morphological adaptations, (b) genetic structure, diversity, and differentiation, (c) reproductive phenology, and (d) floral scents and visitors; we also present an extinction risk assessment of each of the species and their vulnerability to predicted global warming climate scenarios. *How to Save Endangered Magnolias? From Population Biology to Conservation Action… DOI: http://dx.doi.org/10.5772/intechopen.94346*

#### **Figure 1.**

*Current distribution of* Magnolia *sect.* Magnolia *in western México and their occurrence in biogeographic provinces [17]. Except for* M*.* iltisiana *all belong to the* Magnolia pacifica *complex. Undetermined* Magnolia *(*M. *sp).*
