A Study Contrasting Two Congener Plant Species: Psidium guajava (Introduced Guava) and P. galapageium (Galapagos Guava) in the Galapagos Islands
The genus Psidium in Galapagos presents the unique condition of having both an endemic (P. galapageium) and an invasive introduced species (P. guajava). The aim of this study was to evaluate the community structure, morphology, and phenology of both species in San Cristobal Island, which is essential for informing conservation actions.
There are clear morphological differences between the species studied. Flowers and their parts, buds, fruits, and leaves were on average smaller in P. galapageium var. howellii than in P. guajava, and the interspecies population variation was greater than within-individual variation in the same species.
The community-level characterization showed different plant community structures. While plots with P. guajava were dominated by herbaceous species, shrubby species were dominant in the P. galapageium areas. Species composition between plots with P. guajava and P. galapageium showed similarity in the absolute numbers as well as relative proportions of native, endemic, and introduced species over plots of both species. In contrast, species diversity was significantly different, being lower in plots with P. guajava.
Regarding phenology, both P. guajava and P. galapageium displayed similar phenological flowering and fruiting patterns. A complex assortment of floral buds, open flowers, fruitlets, and fruits of varying sizes was found on both species during similar periods.
Finally, a larger array of ecological and biological attributes should be investigated in P. galapageium and P. guajava. It is important to study the species’ reproductive biology, and we need to know if these species are interfertile and produce fertile progeny. In addition, extant populations of both species need to be screened using both morphological and molecular data.
KeywordsGalapagos Psidium galapageium Psidium guajava Endemic plant species Introduced plant species
This research was funded by a grant from GAIAS–Universidad San Francisco de Quito. A research permit (PC-61-14) was granted by the Galapagos National Park that allowed this research to be conducted. I acknowledge Nefi Vélez, Annette Olaya, and Génesis Ponce for their assistance in the fieldwork and data analyses as well as special thanks to the Instituto de Geografïa USFQ (Patricia Martínez and Carlos F. Mena) for the help in designing the maps and to an anonymous reviewer for valuable comments on this manuscript. Thanks to María de Lourdes Torres and Carlos F. Mena for inviting me to participate in this book. Carlos F. Mena and Steve Walsh of the Galapagos Science Center (USFQ/UNC) for their valuable support during the fieldwork. Thanks to all the personnel from GAIAS and the Galapagos National Park Service (specially to Ms. Maryuri Yépez and Mr. Jeffreys Málaga) for their support in the field.
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