qQ 11 C17X NH THE FLORA OF GUADALUPE ISLAND, MEXICO By Reid Moran Published by the California Academy of Sciences San Francisco, California Memoirs of the California Academy of Sciences, Number 19 The pride of Guadalupe Island, the endemic Cisfuiillw giiailulupensis. flowering on a small islet off the southwest coast, with cliffs of the main island as a background; 19 April 1957. This plant is rare on the main island, surviving only on cliffs out of reach of goats, but common here on sjoatless Islote Nccro. THE FLORA OF GUADALUPE ISLAND, MEXICO Q ^ THE FLORA OF GUADALUPE ISLAND, MEXICO By Reid Moran y Published by the California Academy of Sciences San Francisco, California Memoirs of the California Academy of Sciences, Number 19 San Francisco July 26, 1996 SCIENTIFIC PUBLICATIONS COMMITTEE: Alan E. Lcviton. Ediinr Katie Martin, Managing Editor Thomas F. Daniel Michael Ghiselin Robert C. Diewes Wojciech .1. Pulawski Adam Schift" Gary C. Williams © 1906 by the California Academy of Sciences, Golden (iate Park. San Francisco, California 94118 All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any infcMination storage or retrieval system, without permission in writing from the publisher. Library of Congress Catalog Card Number: 96-084362 ISBN 0-940228-40-8 TABLE OF CONTENTS Abstract vii Resumen viii Introduction 1 Guadalupe Island Description I Place names 9 Climate 13 History 15 Other Biota 15 The Vascular Plants Native or Foreign? 19 Goats and Plants 23 Past and Present Vegetation 28 Extinct Plants and Nearly Extinct 39 Composition and Relationships of the Flora 41 Plant Collectors 44 Catalogue of the Plants Ferns 53 Gymnospemis 56 Dicots 66 Monocots 158 Doubtfiil and Excluded Species 168 Acknowledgments 170 Literature Cited 170 Index to Plant Names 185 THE FLORA OF GUADALUPE ISLAND, MEXICO By Reid Moran Department of Botany, California Academy of Sciences, Golden Gate Park, San Francisco, California 94118 Guadalupe Island Is a volcanic oceanic island 260 km west of the peninsula of Baja California, Mevico, and separated by ocean depths of 3600 ni. Its area is 250 km' and its height 1295 ni. Rainfall averages 133 mm near sea level at the south end but evidently is much more at the high north end, where there is no record. For at least a century and a half, feral goats have degraded the island by destroying the vegetation, thus (1) extinguishing native species, (2) fostering soil erosion, and (3) drying up springs by killing trees whose fog drip had added greatly to rainfall. Once-extensive forests of pine, oak, and cypress on the high northern third of the island, and woods of juniper and palms (Brahea), have shrunk drastically and are still shrinking, the remaining old trees unable to reproduce because goats eat the seedlings. Sage scrub (Senecio etc.) in the northern half of the island has been replaced by weedy grasslands, with shrubs surviving only on cliffs and some kinds gradually dying out. Some scrub {Amhrosia. Atriplex. I.yciiiin, Hemizonia) remains at low levels in the drier southern third of the island, where fewer goats range for lack of water. Offshore islets arc refugia for rare plants, including five never found on the main island. The total known vascular flora is 216 species, but not all there at one time: over 30 of them are probably now extinct on the island, and new weeds keep coming as if to take their place. \V hatever we may mean by native on a volcanic oceanic island, I count 45 species, mainly European weeds, as relative newcomers, thus leaving at most 171 to consider as possibly native. However, a dozen of these were first found in parts of the island where earlier collectors had failed to find them. The cumulative evidence is that some must be recent arrivals; but not knowing which are, I keep 15 west American plants in the category of possibly or probably introduced, leaving 156 as less doubtfully native. Of these natives, 34 species and subspecies (21.8 percent) are endemic, including the monotypic genera Baeriopsis J. T. Howell and Hesperelaea A. Gray, though the or more endemics are extinct. Of the native flora. 114 species (73 percent) grow also in Alta California and only eight (5 percent) in Baja California but not northward. In particular, 101 (65 percent) grow on California islands: and 19 of these (12.2 percent) are insular endemics. Of the Guadalupe endemics, six have closest relatives on other islands. Thus the relationships of the Guadalupe flora are mainly to the north, with the islands of southern California: Guadalupe Island is an outlier of the California Floristic Province. It is most important before more plants are lost, to remove all goats from the island, reversing the process of degradation and encouraging in every way the renewal of the natural vegetation. Even at best, some rare plants may die out unless propagated and replanted. Guadalupe Island with its unique flora is a Mexican national treasure in dire need of protection. Received March 3. 1995. Accepted June 6. 1995. Resunien La Isia de Guadalupe is una isia oceanica \nlcanica situada a 260 km al oeste de la peninsula de Baja California, Mexico, y separada por profundidades oceanicas de 3600 ni. Su area es de 250 km cuadrados y su altitud alcan/a 1295 m. La precipitacion pluvial promedia 133 mm eerca del nivel del mar en el extreme sur pero e\idente- mente is mucho mas en el ele\ado extremo norte, donde no existen regislros. Por cuando menos un siglo y medio, las cabras ferales had degradado la isia destruyendo la vegetaeion, de esta manera (I) extinguiendo espeeies nati\as. (2) propiciando erosion del suelo, y (3) secando manantialcs al matar arboles cuya condensacion de niebia complementaba grandemente la lluvia. Los en un tiempo extensos bosques de pinos, encinos, y cipreses, en el elevado tercio norte de la isia. y montes de enebros y palmeras (Bra/iea) se han reducido drasti- camente y continiian reduciendose, los arboles \iejos remanentes imposibilitados para reproducirse por que las cabras de\oran los renuevos. El matorral de salvia {Seitecio etc.) en la mitad norte de la isia, ha sido reempla/ado por male/a de pastizales, con arbustos sobre\i\iendo unicamente en acantilados y algunos gradualmente muriendo. Algiin matorral (Ambrosia. Atriplex, Lyciiim, Hemitonia) permanece a bajos nixclcs en el mas seco tercio del sur de la isia, a donde \an menos cabras por falta de agua. Los islotes litorales son refugios para planlas raras, incluyendo cinco que nunca se han encontrado en la isia principal. La flora vascular total conocida es de 216 espeeies, pero no todas al mismo tiempo: mas de 30 de ellas probablemente se han extinguido ya de la isia, y nuevas malezas siguen llegando como para tomar su lugar. De lo que de alguna manera consideremos nativo en una isia volcanica oceanica, yo recuento 45 espeeies, principalmente malezas europeas, como arribos relativamentc rccicntes, asi dejando cuando mucho 171 que se consideran posiblemente nativas. Sin embargo, una docena de cstas fueron por primera \ez cncontradas en este siglo, en partes de la isia donde no las habian hallado recolectores anteriormente. La evidencia acumulativa es de que algunos son arribos recientes: pero no sabiendo cuales son. yo mantengo 15 plantas oeste-americanas en la categoria de posible o probablemente introducidas. dejando 156 como menos dudosamente nativas. De estas espeeies natiNas, 34 espeeies y subespecies (21.8 por- ciento) son endemicas, incluyendo los generos monotipicos Bueriopsis J. T. Howell v Hespeielaea A. Gray, aunque cinco o mas endemicas estan extinguidas. De la flora nativa, 114 espeeies (73 porciento) crecen tambien en Alta California y imicaniente ocho (5 porciento) crecen en Baja California pero no mas al norte. En particular 101 (65 porciento) crecen en las islas de California; y 19 de cstas (12.2 porciento) son endemicas insulares. De las endemicas de (Juadalupe, seis tienen sus mas cercanas espeeies emparentadas en otras islas. Asi, las relaciones de la flora de Guadalupe se encuentran principalmente al norte, con las islas del sur de California; la isia de (luadalupe es un desplazamiento de la Provincia Floristica de California. Es de la mayor importancia antes de que se pierdan mas plantas, remoxer todas las cabras de la isia, rcvirtiendo el proceso de degradacion y fomentando en todas las formas posibles la recuperacion de la vegetacion natural. En el niejor de los casos, algunas plantas raras no podran sobrevivir a menos que puedan ser propagadas de semillas nativas y replantadas. La isia de Guadalupe con su singular flora, es un tesoro nacional mexicano en de- sespcrada necesidad de proteccion. GUADALUPE ISLAND FLORA Introduction Guadalupe Island, westernmost outpost of Mexico, is a volcanic oceanic island some 260 km (162 statute miles) off the peninsula of Baja Califomia, 337 km (210 miles) southwest of Ensenada, and 400 km (250 miles) south-southwest of San Diego, California (Fig. I ). It is separated from the continent by ocean depths of some 3600 m (2000 fathoms) and evidently has never been connected. Like other high oceanic islands, Guadalupe is remarkable for endemism in the flora and fauna; but it is a naturalists' paradise despoiled by feral goats, housecats, and mice. These pests need to be extemiinated before they destroy more of the unique endemics of this remarkable island; and it is important to reverse the desertification, which in the long mn threatens even the goats themselves. Pending removal of all goats, fenced exciosurcs could help the recovery of rare plants now close to extinction; but even so, some rare ones might not survive unless they could be propagated, of course from native seed, and re- planted.