Stressors/Threats

Relevance to Species

HABITAT LOSS

breeding

Loss of habitat is the primary threat to this species. Suitable habitat consists of more than just the location of individual plants; it needs to account for areas with known populations as well as sufficient area for the species to expand or shift in response to environmental factors. It may be possible, based on habitat preferences and historic distribution, to rate areas based on potential to support future populations, including presence of oxidized soils or gravelly soils, absence of rocky soils and outcrops, elevation, distance to nearest known or historic population, and presence of other cactus species. The Southlands is one of three existing populations centers for this species; the other two being Altar Valley and the area along Ajo Road southwest of Tucson.

dispersal

foraging

wintering

migratory stops

diurnal preferences - day, temporary

diurnal preferences - day, long-term

diurnal preferences - night

fire threat

The impacts of fire on this species are not understood, but thought to be negative. Fire loads in the Southlands are fairly low and, thus, this threat is not as significant as in Altar Valley.

HABITAT ALTERATION

prey

Not applicable

nest sites

Not applicable

vegetation composition/density

Shift toward higher grass and shrub densities through natural succession could reduce cactus densities.

habitat conversion

Shift toward higher grass and shrub densities through natural succession could reduce cactus densities.

escape cover

Not known to be associated with nurse plants; 10 percent or fewer of individuals are found in shade of other plants.

fragmentation

Fragmentation of habitat at arelatively large scale (> 1 km gaps) is thought to dramatically reduce the ability of pollinators to reach the cacti. Lower rates of pollination impact reproductive output and decrease gene flow between populations. Patch size is also important to allow for shifts in location of cacti in response to environmental factors.

HABITAT ALTERATION continued

invasive plant species

Non-native grasses, particularly at high densities, are thought to reduce plant densities. Invasives may also increase risk of fire, which may be detrimental to individual cacti.

invasive animal species

May be trampled by cows and horses.

habitat rehabilitation potential

Habitat rehabilitation potential is high, however, critical factors to restore or enhance to increase suitability for cactus are unknown.

contaminants

Not known

nutrient enrichment

Not known

water accessibility

Apparently irrelevant

drought

Can have a negative, and potentially severe, impact on cactus populations.

flood

Inundation can result in mortality of cacti. Floodplains are poor habitat; although areas of sheet flow are not unsuitable.

groundwater depletion

Apparently irrelevant

root zone water loss

Apparently irrelevant

artificial water sources

Irrigation could provide a real benefit to cactus, especially during droughts. Water should be supplemented during rainy season and only when rain is limited.

infiltration

Apparently irrelevant

runoff

Apparently irrelevant

edge effects

Anecdotal evidence that cactus may like road sides; reasons unknown, but may be linked to potential deterrence of predators. Species also seems to do fairly well in areas with limited disturbance; may be related to reduced competition with other plants. Roads, however, encourage invasive plant species which may have negative impact on cactus.

water quality - turbidity

Apparently irrelevant

water quality - salinity

Apparently irrelevant

water quality - conductivity

Apparently irrelevant

HABITAT ALTERATION continued

water quality - dissolved oxygen

Apparently irrelevant

water quality - effluent

Apparently irrelevant

sheetflow disruption

Apparently irrelevant

flow rate

Apparently irrelevant

land use history

Significance of land use history related to whether seed bank is present. Grazing may potentially have some benefit to extent that grass and shrub densities are lower. Cactus can recover from impact of prior land uses, but only very long periods of time.

roads - dust

Anecdotal evidence that cactus may like road sides; reasons unknown, but may be linked to potential deterrence of predators. Species also seems to do fairly well in areas with limited disturbance; may be related to reduced competition with other plants. Roads, however, encourage invasive plant species which may have negative impact on cactus.

roads - erosion

roads - surface water diversion/ponding

Ponding may increase water availability, benefiting the cactus unless causing prolonged inundation of habitat.

roads - asphalt/contaminants

Not known

SPECIES CHARACTERISTICS

dispersal mechanism

Seed dispersers not known, may include jackrabbits and birds.

behavior traits

Not applicable

habitat rehabilitation potential

Transplanting of cacti has been done, success has not been adequately evaluated and is questionable.

colonization potential

Presence of seed bank critical factor.

effective population size

Not thought to be an issue currently.

total population size

Not thought to be an issue currently.

fecundity

Fairly high, not thought to be an issue.

knowledge/data on species

Very limited

seasonal specialization

Insecticides may be more problematic when blooming. When transplanting, some times of year better than others.

captive breeding/translocation potential

Transplanting of cacti has been done, success has not been adequately evaluated and is questionable.

SPECIES CHARACTERISTICS continued

genetic isolation

Serious in some areas: north of Ajo between Three Points and Casino del Sol and south of the Southlands. The area along I-19 corridor is considered by some to be a lost cause.

inbreeding

Does not seem to self-pollinate.

diurnal specialization

Each flower only open for one day.

off-site mortality - migratory

Not applicable

off-site mortality - from surrounding land uses

Not applicable

breadth of resource use

Not highly specialized with respect to pollinators. Can be found in a wide range of areas, including many that would seem to unsuitable, albeit at very low densities.

sensitivity to disturbance

Does tend to respond favorably to some disturbance, although response may take decades.

adaptability

Reasonably good under certain circumstances, poor under others.

charisma

Low, except valued as collectable.

INTERSPECIFIC FACTORS

predation

Several larval species, rodents, and grasshoppers, among others, known to predate cactus. Areas with high densities of cacti may be especially susceptible.

disease

Susceptible to some type of infection; source unknown, but could be bacterial or related to larval invasion.

pollinators/seed dispersers

Seed dispersers not known, may include jackrabbits and birds. Not highly specialized with respect to pollinators. Pollinator visits decrease dramatically as distance between cacti exceeds 1 km.

competition

Does not like competition. Found in lower densities in areas with dense grasses.

brood parasitism

Not applicable

domestic/feral animals

May be trampled by cows and horses.

invasive species

Non-native grasses, particularly at high densities, are thought to reduce plant densities. Invasives may also increase risk of fire, which may be detrimental to individual cacti.

ANTHROPOGENIC FACTORS

edge effect

Anecdotal evidence that cactus may like road sides; reasons unknown, but may be linked to potential deterrence of predators. Species also seems to do fairly well in areas with limited disturbance; may be related to reduced competition with other plants. Roads, however, encourage invasive plant species which may have negative impact on cactus.

disease

Susceptible to some type of infection; source unknown, but could be bacterial or related to larval invasion.

fire threat

The impacts of fire on this species are not understood, but thought to be negative. Fire loads in the Southlands are fairly low and, thus, this threat is not as significant as in Altar Valley.

off-road vehicles - dust

Run over fairly frequently by ORVs. ORV disturbance may also encourage invasive plant species which may have negative impact on cactus.

off-road vehicles - erosion

off-road vehicles - noise

mining

Has resulted in loss of large numbers of plants. Also likely to completely remove or serious impact seed bank.

passive recreation

People moving off of trails may expose cacti to potential disturbance, trampling, or risk of collection.

grazing - vegetation impacts

Not known

grazing - soil impacts

collection/hunting

Collection is a problem; highly valued by collectors in Germany and Japan.

herbicides

Not highly specialized with respect to pollinators. Non-target insecticides may be a problem.

insecticides

pesticides - impacts to species

pesticides - impacts to prey

direct take/mortality

Primarily associated with loss of habitat and collection.

noise

Apparently irrelevant

light

Apparently irrelevant

movement

Apparently irrelevant

ANTHROPOGENIC FACTORS continued

landscaping

Impact of using non-native species as landscaping on cacti unknown, but generally thought to be a risk. The species can be used in landscaping, however, this is not a replacement for preservation of the species in its native habitat. Use for landscapeing, however, could provide connectivity between isolated reserves for pollinators which tend to be limited to hops of no more than 1 km between plants.

invasives

Non-native grasses, particularly at high densities, are thought to reduce plant densities. Invasives may also increase risk of fire, which may be detrimental to indivdual cacti.

domestic/feral animals

Not considered a problem

dumping

Not considered a problem

undocumented immigrants

Not considered a problem

increased road density

Results in loss of habitat.

road kill

May be run over by off-road vehicles.

electrocution on powerlines/towers

Not applicable

CONNECTIVITY

fragmentation

Fragmentation of habitat at a a relatively large scale (> 1 km gaps) is thought to dramitcally reduce the ability of pollinators to reach the cacti. Lower rates of pollination imapct reproductive output and decrease gene flow between populations. Patch size is also important to allow for shifts in location of cacti in response to environmental factors.

barriers

Not considered a problem

traffic volumes

Not considered a problem

wash incision

If gradual, may provide habitat for cactus; typically headcuts result in loss of habitat.

corridor width

Minimim patch size not known.

habitat patchiness

Over entire landscape, a mosaic of habitat types and locations is desirable, as long as individual reserves are not isolated.

riparian/upland connection

Suitability highly variable.

road crossings

Not considered a problem

road width

Not considered a problem

vegetation next to roads

Non-natives may pose fire threat or competition.