Prey Substitution in the Atlantic Forest: Why Mosquitoes Are Swapping Wildlife for Urban Biomass

1. Introduction: The Anthropocene and the Biological Siege

The history of human civilization is, in many respects, a history of ecological restructuring. From the Neolithic Revolution to the industrial sprawl of the twenty-first century, our species has systematically altered the biosphere to maximize resource extraction and settlement space. However, this domination of the landscape has precipitated a cascade of unintended biological consequences, nowhere more acute than in the microscopic wars waged at the interface of human and wildlife populations. We exist in the epoch of the Anthropocene, a geological age defined by human influence, but biologically, we are entering the age of the "Generalist." As we simplify complex ecosystems, stripping away the specialized flora and fauna that evolved over millennia, we unwittingly select for organisms that are adaptable, opportunistic, and often parasitic. Among these, the mosquito (Diptera: Culicidae) stands as the preeminent beneficiary of our ecological mismanagement.

The Atlantic Forest (Mata Atlântica) of Brazil serves as the ultimate laboratory for this transformation. Once a continuous, verdant ribbon stretching over 1.3 million square kilometers along the South American coastline, it has been reduced by centuries of colonization, urbanization, and agriculture to a fragmented archipelago of forest islands. Today, less than 30% of its original cover remains, much of it existing in isolated patches surrounded by a hostile matrix of pasture, sugarcane, and concrete.¹ This degradation is not merely a loss of carbon stock or aesthetic beauty; it is a fundamental dismantling of the biological barriers that once kept zoonotic pathogens at bay.

Recent research, specifically a landmark 2026 study published in Frontiers in Ecology and Evolution by Alencar, Machado, and colleagues, has illuminated a disturbing mechanism within this ecological collapse: the behavioral plasticity of mosquitoes. The study reveals that as biodiversity declines—as the tapirs, monkeys, and forest birds vanish from these forest remnants—the mosquitoes that once fed upon them do not disappear. Instead, they turn their sensory apparatus toward the most abundant remaining biomass: Homo sapiens. This shift from zoophagy (animal-feeding) to anthropophagy (human-feeding) is not accidental. It is a calculated survival strategy driven by the "convenience" of human availability and the desperation of an "empty forest".²

This report provides an exhaustive analysis of this phenomenon. We will traverse the molecular biology of mosquito olfaction, exploring how dopamine-mediated learning allows insects to "switch" targets in a single generation. We will examine the specific vector species implicated—Aedes scapularis, Psorophora ferox, and the enigmatic Coquillettidia venezuelensis—and dissect their potential to bridge the gap between sylvatic viruses and human populations. Furthermore, we will contextualize these findings within the broader theoretical framework of disease ecology, debating the "Dilution Effect" versus the "Amplification Effect," and drawing parallels with similar ecological unravelings in the malaria belts of Southeast Asia and the tick-infested forests of India. The evidence suggests that we are not merely witnessing a passive loss of biodiversity, but actively engineering an environment that selects for the hyper-transmission of disease.

2. The Atlantic Forest: A Fragmented Archipelago

To understand the behavior of the mosquito, one must first understand the stage upon which it acts. The Atlantic Forest is one of the world's top biodiversity hotspots, historically hosting a vertebrate richness that rivals the Amazon. However, its geography—hugging the coastline where the vast majority of Brazil's human population resides—has made it the frontline of development since the 16th century.

2.1 The Ecology of Fragmentation

The current state of the Atlantic Forest is defined by "fragmentation geometry." Unlike a large continuous block, the remaining forest exists as thousands of small patches. This geometric alteration fundamentally changes the rules of life for the organisms within.

• The Edge Effect: As a forest block becomes smaller, the ratio of "edge" to "interior" increases. The edge is a distinct ecological zone characterized by higher temperatures, lower humidity, increased wind shear, and higher light penetration compared to the deep forest.⁴ For hematophagic insects, the edge is a zone of high stress but also high opportunity. It is here that the vertical stratification of the forest collapses. In the deep forest, distinct mosquito communities inhabit the canopy (feeding on monkeys) and the ground (feeding on rodents). At the edge, these worlds crash together, bringing canopy vectors like Haemagogus down to ground level where they may encounter humans.⁶

• Defaunation: The "Empty Forest" syndrome is prevalent in these fragments. While the trees may remain standing, the medium-to-large mammals—agoutis, pacas, howler monkeys, and jaguars—are often hunted out or cannot sustain viable populations in small patches. This phenomenon, known as defaunation, creates a "blood famine" for zoophilic mosquitoes.²

2.2 The Study Sites: A Tale of Two Reserves

The research by Alencar et al. (2026) focused on two distinct remnants in the state of Rio de Janeiro, offering a comparative look at mosquito behavior in landscapes with varying degrees of preservation.¹

2.2.1 Guapiaçu River Ecological Reserve (REGUA)

Located in the municipality of Cachoeiras de Macacu, REGUA represents the "best-case scenario" for the region. Spanning approximately 7,400 hectares, it is a continuous tract of forest that supports a complex vertical structure and high biodiversity. It is home to over 455 bird species and 61 mammal species, including the woolly spider monkey (southern muriqui) and elusive felids.⁸

• Ecological Significance: In REGUA, the "Dilution Effect" should theoretically be functional. The abundance of birds, amphibians, and mammals provides a diverse array of blood meal options, theoretically diluting the biting pressure on any single species (including humans) and regulating pathogen transmission through the presence of "incompetent" hosts.⁸

2.2.2 Sítio Recanto Preservar (SRP)

In contrast, SRP in Silva Jardim represents the more common reality of the Atlantic Forest: a smaller, secondary forest fragment embedded in a matrix of rural development. While it features a dense shrub layer and tall trees, it is a "restored" environment, heavily influenced by its proximity to human habitation and agriculture.⁸

• Ecological Significance: Here, the edge effects are more pronounced. The buffer between the sylvatic cycle and the peridomestic cycle is thin. This site serves as a sentinel for the "convenience" hypothesis—where mosquitoes, deprived of the rich mammalian diversity found in REGUA, might turn to the constant presence of humans managing the land or residing nearby.³

3. The Frontiers Study: Methodology and Revelation

The central inquiry of the study was simple yet profound: In these remnants, what are the mosquitoes eating? Answering this requires overcoming the "cryptic" nature of mosquito feeding. A mosquito caught in a trap tells you where it is, but not who it bit. To solve this, the researchers employed molecular forensics.

3.1 Methodological Rigor: The Molecular Barcode

The research team, led by Dr. Jeronimo Alencar, utilized CDC light traps positioned at a height of 2 meters. This height is strategic; it captures the "interface" zone where ground-dwelling humans and low-flying sylvatic mosquitoes intersect. The traps operated during the crepuscular period (twilight), a critical window of activity for many vector species.⁸

From the catch of over 1,700 mosquitoes, the team isolated the "engorged" females—those that had recently taken a blood meal but had not yet fully digested it. This digestion clock is rapid; researchers have only a defined window (often 24-48 hours) before the host DNA is degraded by the mosquito's enzymes.

• DNA Sequencing: The researchers extracted DNA from the mosquito stomachs and targeted the cytochrome b (Cytb) gene. This mitochondrial gene evolves rapidly enough to distinguish between closely related vertebrate species. By amplifying this gene and comparing the sequence to a reference database (BLAST), they could identify the specific host.⁸

• Precision: The technique distinguishes Homo sapiens from Alouatta guariba (Howler monkey) or Canis lupus (domestic dog), providing a high-resolution map of the trophic network.³

3.2 The Findings: A Clear Anthropophilic Signal

The results were stark. Despite being located in nature reserves, where one might expect mosquitoes to feed on rodents, marsupials, or birds, the primary host identified was humans.

• The Numbers: Of the blood meals that could be successfully identified, 75% were human. DNA traces from 18 different humans were detected in the mosquito stomachs.³

• The Species: This was not limited to the notorious "domestic" mosquito Aedes aegypti. The human blood was found in sylvatic and peri-sylvatic species including Aedes scapularis, Psorophora ferox, and Coquillettidia fasciolata.

• Secondary Hosts: Birds were the second most common host (six individuals), followed by rare instances of amphibians, rodents, and canids.³

3.3 The Phenomenon of Mixed Meals

Perhaps the most scientifically significant finding was the detection of "mixed meals"—mosquitoes containing blood from two different species simultaneously.

• The Evidence: Coquillettidia fasciolata specimens were found containing both human and bird blood. Coquillettidia venezuelensis was found containing both human and amphibian blood.¹

• The Implication: A mixed meal is the biological equivalent of a dirty needle shared between species. It proves that a single individual mosquito is biting a wildlife host and then, within the same feeding cycle or a subsequent one, biting a human. This is the definition of a "bridge vector." If that bird was viremic with St. Louis Encephalitis, or that amphibian carried an undocumented alphavirus, the path to the human bloodstream is open and direct.⁸

4. The Ecological Engine: Dilution, Amplification, and the Edge

The findings from Rio de Janeiro do not exist in a vacuum; they feed into one of the most spirited debates in disease ecology: Does biodiversity protect us, or does it endanger us?

4.1 The Dilution Effect Hypothesis (DEH)

Proposed by Ostfeld and Keesing, the Dilution Effect Hypothesis suggests that high biodiversity reduces the risk of disease transmission. The logic follows a vector-centric view of the world.

• The Mechanism of Wasted Bites: In a pristine forest, a generalist mosquito encounters a vast array of hosts: opossums, squirrels, lizards, tanagers, and monkeys. Many of these are "incompetent reservoirs"—meaning if the mosquito injects a virus into them, the virus cannot replicate to high enough levels to be passed on. These hosts act as "sinks," absorbing mosquito bites and breaking the chain of transmission.

• The Mechanism of Regulation: Diverse communities include predators (dragonflies, bats, spiders) and competitors that regulate the population density of vectors.¹¹

In the context of the Atlantic Forest study, the high prevalence of human blood meals suggests a failure or loss of the dilution effect. As the diverse "sink" hosts are removed via deforestation and hunting, the mosquitoes are not encountering the protective shield of biodiversity. Their bites are no longer "wasted" on incompetent squirrels; they are concentrated on the few remaining species.

4.2 The Concentration (or Rescue) Effect

When biodiversity collapses, the remaining hosts are often those most resilient to human disturbance: rats, certain generalist birds, and humans ourselves. If these remaining hosts are competent reservoirs (or if the target is the human, who is the victim of interest), the risk skyrockets.

• The "Convenience" Factor: Dr. Machado's assertion that mosquitoes feed on humans "out of convenience" aligns with the "Rescue Effect." The mosquito population, facing a crash in their traditional food supply, is "rescued" from starvation by the anthropogenic biomass. Humans effectively replace the extinct megafauna as the primary protein source for the forest's insects.²

4.3 Anthropogenic Edge Effects and Vertical Collapse

The physical degradation of the forest exacerbates this trophic shift. The "Edge Effect" alters the microclimate, creating hotter, drier conditions that favor specific mosquito species while eliminating others.

• Vertical Stratification: In deep forests, Anopheles cruzii and Haemagogus species are strictly arboreal, staying in the canopy to bite monkeys. However, studies in fragmented Atlantic Forests show that as the canopy becomes discontinuous and the edge environment encroaches, these mosquitoes descend to the ground level.⁶

• The Mechanism: The study by Alencar captured mosquitoes at 2 meters—ground level. The presence of typically sylvatic or canopy-associated genetics in these traps confirms this vertical collapse. Humans, walking on the ground, are suddenly accessible to the entire vertical column of the mosquito assemblage.⁶

5. Profiles in Adaptation: The Vector Assemblage

The generic term "mosquito" hides a complex taxonomy of behaviors. The study highlighted specific species that are acting as the agents of this shift. Understanding their biology is key to understanding the risk.

5.1 Aedes scapularis: The Adaptive Conqueror

If there is a protagonist in the story of Atlantic Forest epidemiology, it is Aedes scapularis.

• Ecological Niche: Historically, Ae. scapularis is a woodland mosquito, breeding in temporary, rain-filled ground pools. It is known for its desiccation resistance, allowing it to survive the hotter, drier conditions of forest edges and open pastures.¹⁵

• The Shift: The study confirms its presence in the "human-feeding" cohort. This aligns with historical data showing its ability to invade peridomestic spaces. Unlike Aedes aegypti, which is strictly urban, Ae. scapularis is a "commuter," moving between the forest and the home.¹⁷

• Viral Competence: This species is a loaded gun. It has been found naturally infected with Yellow Fever Virus (YFV) during the 2016-2017 outbreaks in southeastern Brazil.¹⁸ It is also a competent vector for Rocio virus and Venezuelan Equine Encephalitis (VEE). Its confirmed shift toward human feeding in biodiversity-poor areas creates a direct highway for these viruses to exit the forest cycle.¹⁹

5.2 Psorophora ferox: The Aggressive Bridge

• Morphology and Behavior: Psorophora ferox is a large, striking mosquito with white-tipped legs (giving it the moniker "white-footed woods mosquito" in some regions). It is an aggressive, persistent biter that is active during the day and at twilight.

• Trophic Plasticity: While traditionally feeding on woodland mammals, the detection of human DNA in Ps. ferox stomachs in the Frontiers study highlights its opportunistic nature. It does not ignore a human host; it actively pursues them.¹⁶

• Risk Profile: Ps. ferox is a known carrier of the Rocio virus (ID50 comparable to Ae. scapularis) and Ilheus virus. While its population densities are often lower than Culex or Aedes, its large blood meal size and aggressive persistence make individual bites high-risk events.²⁰

5.3 Coquillettidia venezuelensis: The Amphibian Anomaly

The most biologically intriguing finding is the behavior of Coquillettidia venezuelensis.

• Larval Biology: Unlike most mosquitoes that breathe air at the water surface, Coquillettidia larvae have modified siphons that pierce the roots of aquatic plants (like water lettuce, Pistia) to obtain oxygen. This makes them immune to surface films or predators that hunt at the waterline.²³

• The Amphibian Link: The study found this species feeding on both humans and amphibians.¹ This is rare. Most mosquitoes are strictly mammal/bird feeders or strictly reptile/amphibian feeders. A mosquito that crosses the Class barrier (Amphibia to Mammalia) is an "inter-class bridge."

• Epidemiological Shadow: Amphibians are reservoirs for diverse and often understudied viruses. The ability of Cq. venezuelensis to bridge this gap, alongside its known competence for Oropouche virus (OROV), introduces a variable into the transmission equation that is currently unquantified and largely unmonitored.⁸

5.4 Haemagogus and Sabethes: The Absent Giants

While the study focused on ground-level captures, the "ghosts" of the canopy—Haemagogus janthinomys and Sabethes species—are relevant by their absence or displacement. These are the primary vectors of sylvatic Yellow Fever. Their survival depends on high canopies and primate populations. As biodiversity loss removes the primates, these mosquitoes must either perish or adapt. The fear, supported by the plasticity seen in Ae. scapularis, is that Haemagogus may also begin to dip lower, seeking humans as the monkeys vanish.⁹

6. The Neurobiology of Shift: How Mosquitoes "Learn" Humans

How does a mosquito "decide" to switch from a capybara to a human? It is not merely a matter of bumping into a new host; it involves a sophisticated neurobiological recalibration of the olfactory system.

6.1 The Olfactory Landscape of the Host

Mosquitoes inhabit a world of chemical plumes. Host seeking is a multimodal sequence:

1. Activation (Long Range >10m): Carbon dioxide (CO2) is the universal wake-up call. It triggers "anemotaxis"—upwind flight.²⁶

2. Orientation (Mid Range): Visual cues (dark shapes) and specific odor blends guide the approach.

3. Landing (Short Range <1m): This is where specificity occurs. Human skin is chemically unique among mammals. We produce high levels of L-(+)-lactic acid and short-chain carboxylic acids, byproducts of our specific skin microbiota (Corynebacterium, Staphylococcus) breaking down our sweat.²⁶

6.2 The Dopaminergic Mechanism of Learning

It was long assumed that mosquito preferences were hard-wired (innate). However, recent research has shattered this dogma. Mosquitoes possess the capacity for associative learning, mediated by the neurotransmitter dopamine in the antennal lobe of the brain.

• The Mechanism: When a mosquito successfully feeds, the ingestion of blood provides a massive nutritional reward. This triggers a release of dopamine. If this dopamine release coincides with a specific odor profile (e.g., the carboxylic acid blend of a human), the mosquito's brain forms a positive association.

• Training the Vector: In the context of the Atlantic Forest, deforestation acts as a "training camp." If humans are the only abundant host, young mosquitoes that successfully feed on humans receive this dopamine "reward" signal. Those that try to find scarce monkeys may fail and starve. Consequently, the surviving population is "trained" via dopaminergic reinforcement to prioritize human scent.²⁸

• Genetic Selection: Over multiple generations, this behavioral conditioning can transition into genetic selection. Variants with higher expression of receptors sensitive to human odors (such as the Ir8a co-receptor, essential for lactic acid detection) may outcompete those tuned to generic mammalian scents.²⁷

6.3 Plasticity as an Epidemiological Force

This neurobiological plasticity explains why the "convenience" hypothesis holds true. The mosquito is not a rigid machine; it is a learning organism. The "empty forest" deprives them of the "monkey signal," while the encroaching human settlement provides a constant, reinforced "human signal." The result is a vector population that is neurobiologically tuned to the human signature.³¹

7. The Viral Payload: Arboviruses on the Edge

The shift in mosquito feeding behavior is the fuze; the viral payload is the explosive. Brazil's recent history is a testament to the volatility of this system.

7.1 Yellow Fever: The Sylvatic Spillover

Between 2016 and 2018, Brazil experienced its worst Yellow Fever outbreak in 80 years, spreading from the Amazon/Cerrado into the Atlantic Forest. The virus killed hundreds of humans and decimated primate populations (some estimates suggest thousands of monkeys died).

• The Cycle: Traditionally, YFV is a sylvatic virus (Haemagogus mosquitoes  Primates). Humans are accidental hosts.

• The Breakdown: The Frontiers study's confirmation of Aedes scapularis feeding on humans in forest remnants provides the mechanism for the next wave. If Ae. scapularis can bridge the gap—maintaining the virus in low-density primate populations or vertical transmission, and then biting humans—it creates a "peridomestic" bridge that bypasses the strict sylvatic requirement.¹⁸

7.2 Oropouche Virus (OROV): The Silent Surge

Oropouche virus is currently surging in South America (2024-2025). Known as "sloth fever," it causes debilitating symptoms. It is transmitted by Culicoides midges but also by mosquitoes.

• The Threat: The identification of Coquillettidia venezuelensis and Aedes serratus as potential vectors that act as bridges (feeding on sylvatic hosts and humans) suggests OROV could establish a foothold in the Atlantic Forest periphery. The "mixed meal" finding (human/amphibian) in Cq. venezuelensis is particularly worrying if amphibians act as maintenance hosts or if the mosquito's generalist nature allows it to tap into cryptic mammalian reservoirs.²⁴

7.3 Rocio Virus: The Sleeping Giant

In the 1970s, the Rocio virus caused a severe encephalitis epidemic in the Ribeira Valley (Atlantic Forest). It disappeared as mysteriously as it arrived. It is believed to be an avian virus.

• The Connection: The study found Coquillettidia fasciolata feeding on birds and humans. Psorophora ferox (a competent Rocio vector) was found feeding on humans. The ecological machinery for a Rocio resurgence—vectors that bite the avian reservoir and the human host—remains intact and active.²⁰

7.4 Vector Capacity ()

To quantify this risk, epidemiologists use the Vector Capacity equation:

• (): Density of mosquitoes.

• (): Biting rate on humans.

• (): Daily survival rate.

• (): Extrinsic incubation period of the virus.

The findings of Alencar et al. directly impact the variable () (human biting rate). By shifting preference from animals to humans, the parameter () increases. Since () is squared in the equation (because the mosquito must bite once to get infected and again to transmit), a linear increase in human feeding preference results in an exponential increase in vector capacity.³⁶

8. Global Parallels: Asia, India, and the Amazon

The Atlantic Forest is a microcosm of a global phenomenon. The "Biodiversity-Disease" relationship is playing out in parallel theaters across the tropics.

8.1 Southeast Asia: The Knowlesi Shift

In Malaysian Borneo, the deforestation for palm oil has led to the emergence of Plasmodium knowlesi, a macaque malaria, in humans.

• The Parallel: Just as in Rio, the fragmentation of forests forces the reservoir (macaques) and the vector (Anopheles balabacensis) into the same edge habitats as humans.

• The Difference: In Borneo, the vector remains zoophilic but bites humans due to extreme proximity (the "accidental" host). In the Atlantic Forest, the data suggests Aedes scapularis and others may be undergoing a functional shift in preference due to the lack of alternatives.³⁷

8.2 India: Kyasanur Forest Disease (KFD)

In the Western Ghats of India, the clearing of forests for cashew plantations disrupted the tick-monkey cycle of KFD.

• The Mechanism: Deforestation reduced the diversity of large mammals but increased the density of small rodents and shrews (competent reservoirs for the tick). This "Amplification Effect" mirrors the loss of dilution seen in Brazil. The ticks, starving for large hosts, turned to the cattle and humans entering the forest interface.³⁹

8.3 The Amazon: The Frontier of Spillover

In the Amazon basin, land-use change is converting rainforest to soy and cattle pasture. This drives vectors like Nyssorhynchus darlingi (malaria) and Haemagogus (YFV) into settlements. The Atlantic Forest serves as a "crystal ball" for the Amazon—showing what happens when the fragmentation process reaches its mature, terminal phase.⁴¹

9. Synthesis: The Future of the Human-Vector Interface

The report from the Atlantic Forest is not merely a catalog of mosquito bites; it is a forecast of the Anthropocene's epidemiological weather. The data supports a grim conclusion: Biodiversity loss is an active driver of disease emergence.

9.1 The "Training" of the Vector

We are effectively breeding a new class of vector. By removing the "buffer" species—the sloths, the tanagers, the agoutis—we are forcing the mosquito's evolutionary hand. We are removing the "incompetent" hosts that diluted disease risk and leaving only the "competent" or "susceptible" hosts (humans and synanthropic rodents). Through dopaminergic learning and natural selection, we are training sylvatic mosquitoes to become urban terrorists.

9.2 The Homogenization of Risk

As urban heat islands expand and forests shrink, the microclimates of the world are homogenizing. This favors a specific guild of mosquitoes: the generalists, the desiccation-resistant, the anthropophilic. Aedes scapularis and Aedes albopictus are the winners of this new world order. The losers are the specialists, and with them, the ecological safety net that kept sylvatic viruses in the trees.⁴²

9.3 Recommendations for Surveillance and Management

1. Sentinel Surveillance: Monitoring must move beyond the city center. We need "edge surveillance"—trapping at the forest interface to detect when sylvatic species like Ae. scapularis begin to dominate human biting collections.

2. Molecular Triage: Blood-meal analysis (DNA barcoding) should be a standard protocol, not just a research luxury. Knowing what mosquitoes are eating is as important as knowing where they are.

3. Ecological Restoration with Caution: Reforestation is vital, but "greenwashing" urban areas without restoring functional biodiversity (predators and diverse hosts) can create "vector islands." Restoration must aim for trophic complexity, not just tree cover.⁴⁴

In the final analysis, the mosquito is a mirror. Its changing behavior reflects our changing landscape. The thirst for human blood documented in the remnants of the Atlantic Forest is a symptom of a planet where the wild is receding, and the boundaries between the human and the non-human are collapsing. If we continue to simplify the web of life, we should not be surprised when the remaining strands entangle us.

10. Data Supplement: Structured Ecological Analysis

Table 1: Comparative Vector Ecology in Atlantic Forest Remnants

Analysis of key species identified in Alencar et al. (2026) and supporting literature.

Species	Primary Niche	Host Plasticity Index	Anthropogenic Risk Factor	Virological Competence
Aedes scapularis	Ground pools, Forest Edge	High: Shifts readily between mammals and humans.	Critical: Invades peridomestic spaces; desiccation resistant.	High: Yellow Fever, Rocio, VEE, Ilheus.8
Psorophora ferox	Flooded Woodlands	Medium: Aggressive generalist but prefers woodland cover.	High: Persistent biter; large blood meal size.	Medium: Rocio, Ilheus; potential WNV bridge.20
Coquillettidia venezuelensis	Aquatic Vegetation (Root breathing)	Extreme: Feeds on Mammals, Amphibians, Humans.	Unknown/Emerging: Larvae hard to control; unique host bridging.	Emerging: Oropouche (OROV), WNV, EEE.8
Aedes albopictus	Peri-urban / Edge	High: Opportunistic.	Severe: Invasive species; outcompetes natives.	Severe: Dengue, Zika, Chikungunya, YF.8
Haemagogus janthinomys	Canopy (Primary Forest)	Low: Strictly arboreal (usually).	Conditional: Risk increases if canopy collapses (vertical migration).	Critical: Primary vector of sylvatic Yellow Fever.9

Table 2: The Dilution Effect vs. The Reality of Fragmentation

Contrasting theoretical ecological protection with the observed data from Rio de Janeiro.

Mechanism	Theoretical "Dilution Effect" (Pristine Forest)	Observed "Fragmentation Reality" (Atlantic Forest)	Consequence
Host Diversity	High (Birds, Rodents, Primates, Marsupials).	Low (Defaunated; few generalist species remain).	Mosquitoes lose "sink" hosts; biting pressure concentrates on remaining species (Humans).
Encounter Rate	Bites distributed across many "incompetent" hosts.	Bites focused on "competent" or "dead-end" but susceptible hosts.	Increased transmission of zoonoses; increased human nuisance and allergy burden.
Vector Regulation	Predation by diverse insectivores (bats, birds) limits density.	Loss of specific insectivores releases vector populations.	Higher vector density () in the Vector Capacity equation.
Olfactory Learning	Mosquitoes encounter diverse scents; generalist behavior rewarded.	Mosquitoes encounter primarily human scent; anthropophagy rewarded.	Evolution of highly efficient human-seeking behaviors (Dopaminergic reinforcement).

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