Two types of sites are typical for this species. One, along the coast in "huayco" (flash flood)
situations from 50 to 700 m in soils that are sandy loam or clay in texture. The other more common
location is roadsides, mountain slopes, and washes (up to 1600 m) that drain into valleys of the
Pacific watersheds. The latter sites are sandy to stony with rocks normally present. Most sites are
extremely or very dry -- a striking feature now being exploited in a drought-tolerance improvement
program (Rick, unpublished).
The most common associate of S. pennellii is Loaza spp., particularly between 500 and 1200 m
elevation; in fact, these Loaza spp. are so consistent as indicator plants that they have seldom failed
to lead to useful seed collection of S. pennellii. Columnar cacti are common from 600-1000 m in the
northern part of the distribution from Chicama to Chillon. An unidentified yellow-flowered legume is
the characteristic companion plant. Another association to be verified is a Mirabilis-like species
(Nyctaginaceae) mentioned twice in collections north of Huaura. Sympatry with L. peruvianum has
been recorded several times from Huaura to Pisco, 500-1600 m. L. hirsutum has been found only at
Espíritu Santa (Lurín watershed). The only instance of S. pennellii as the dominant vegetation
element is Sayan-Churín (DHUNA 1001, 1013), where it was observed on a mountainside after the
rainy season of 1972. L. pimpinellifolium was also present here in the lower slopes above the
irrigation ditches and close to the pennellii plants.
II. DESCRIPTION OF THE COLLECTIONS ARRANGED BY WATERSHEDS AND LOMAS
1. Watersheds: Tumbes, Chira, and Piura
(Table 5, fig. 2)
The two northernmost watersheds on the coast of Perú (Tumbes and Chira) have their origins in
Ecuador. They belong to the zone of transition to tropical conditions and the rivers have water the year
around. The Tumbes watershed has not been well collected with regards to Lycopersicon spp. As shown
in Table 5, only one herbarium specimen, L. peruvianum, is included Expedition for 1974 in western
South America) collected accessions of the red-fruited L. pimpinellifolium from this area. Since there is a
planned project for irrigation and development of the Puyango (Ecuador)-Tumbes (Perú) area during
l976-1986, there is danger of major disturbance of this natural habitat.
The Chira watershed is one of the largest of the Peruvian coast if the tropical area that corresponds
to Ecuador is included. Like Tumbes, it also has a year-around water supply and is not well known
floristically. The valley can be divided into 2 basic areas: a) a desert coast delta (0-300 m) with a very
narrow (2-4 kms on each side) vegetation strip along the river which is dedicated to irrigated farming
(Pima cotton, citrus, coconuts, rice, bananas); and b) a transition zone from dry through annual
intermittent rain flora to tropical southern Ecuador conditions where cattle grazing is the most common
activity. This area ranges from 300 to 2500 m.
The Piura river basin can be divided into two distinct zones: a) the desert zone, where the river flows
west from Chulucanas for approximately 150 km; and b) the mountain zone starting in the Chulucanas-
Morropon area at 500-1000 m and ending in Huarmaca at 2500 m.
This valley has an intermittent water supply based on varied rainfall that occurs between December
and April. While the mountain zone gets yearly rains, the desert has fewer rainy years but these usually
produce a very profuse annual flora that can support cattle for 2 to 3 dry years. The river dries up
usually around the Chulucanas area; but at the Quebrada de San Francisco, water from the Quiroz river
(Chira basin) was diverted into the Piura in 1954. In 1976 another diversion from the Chira was finished.
Thus, natural and farming conditions are changing, and it is possible that the area below the continuous
water source now has a mixed vegetation from the two basins. The main crops in the middle and lower
sections are long-staple cotton, corn and sorghum; and in the higher watershed, rice, cotton, fruits
(mango, citrus, avocado) and coffee. This is the only coastal valley where cattle can be raised on pastures
based on the intermittent desert vegetation.
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