Island and random encounters tables speciation.

This is inspired from this youtube video about how species fill vacant ecological niches on isolated islands. For exemple how kiwi birds took on the role and characteristics of rats in the absence of these mammals.

Let try to apply this on random encounter tables. Now random encounter tables are not really ecologies or biomes but since we are familiar with their content it can be fun to generate interesting variants.

Let use the the Forest/Wooded encounters from the Labyrinth Lord's Wilderness Monster Encounter Table.

Forest/Wooded encounters (1d20)

1. Bee, giant killer
2. Boar
3. Bugbear
4. Cat, Panther
5. Cockatrice
6. Dryad
7. Dragon, Green
8. Elf
9. Ghoul 
10. Hobgoblin
11. Werewolf
12. Brigands
13. Orc
14. Roc, small
15. Spider, giant crab
16. Troll
17. Unicorn
18. Wight 
19. Wolf
20. Wolf, dire

Let remove half the encounters so that the "surviving" monsters can fill their "niches".

We roll 10d20: 20 - 11 - 2 - 17 - 20 - 5 - 12 - 12 - 6 - 4 (re rolling doubles: 7, 10)

1. Bee, giant killer
2. Boar
3. Bugbear
4. Cat, Panther
5. Cockatrice
6. Dryad
7. Dragon, Green
8. Elf
9. Ghoul 
10. Hobgoblin
11. Werewolf
12. Brigands
13. Orc
14. Roc, small
15. Spider, giant crab
16. Troll
17. Unicorn
18. Wight 
19. Wolf
20. Wolf, dire

Now let see who fill these empty niches

For each absent monster we assign a random survivor who will speciate to fill it empty niche, we will combine the two monsters to create a new one. This new monster use the survivor stats bloc and switch 2d3 characteristics with the monster it is replacing.

Characteristics table (d12)

1. No.Enc
2. Alignment
3. Movement
4. Armor Class
5. HD (size) 
6. Attack type
7. Damage
8. Saves
9. Morale
10. Hoard class
11. Special ability or vulnerability 
12. Appearance  

If we make the rolls we end up with:

1. Boar wight 
2. Panther trolls  
3. Cockatrice elves 
4. Dryad bugbears 
5. Green dragon ghouls 
6. Hobgoblin wolfs 
7. Werewolf bugbears 
8. Brigands giant killer bees 
9. Unicorn giant killer bees 
10. Dire wolf wolf (??) 

What happen to the original survivor monsters?
Let roll on the adaptation table to find out:

Adaptation table (d8)

• 1-2 Dwarf variant (-1 HD, step up No Enc.) 
• 3-4 Giant variant (+1 HD, step down No Enc.) 
• 5-6 Random characteristic variant (roll on the characteristic table and modify this characteristic to create a variant)
• 7 Stunted variant (roll on the characteristic table and nerf or dilute this characteristic)  
• 8 Hyper variant (roll on the characteristic table and boost or intensify this characteristic) 

If we make the rolls we end up with:

1. Giant giant killer bee
2. Hyper Bugbear (Hyper variant: boost number encountered!)
3. Dwarf Elf
4. Giant Ghoul 
5. Dwarf Orc
6. Dwarf small Roc  
7. Giant giant spider crab  
8. High Damage Trolls (Hyper variant: boost damages!) 
9. Giant Wight 
10. Climbing Wolf (Random characteristic variant: movement type) 

Our final forest island random table: 

d20

1. Giant Wight 
2. Boar Wights (tusked wights who search the ground with their big groin) 
3. High Damage Trolls (ouch!)
4. Panther Trolls (stealthy four legged trolls)  
5. Dwarf Elves
6. Cockatrice Elves (use petrification to craft stuff out of petrified victims) 
7. Hyper Bugbear (larger No. Enc.) 
8. Dryad Bugbears (tree linked female bugbears) 
9. Werewolf Bugbears (bugbears who turn into dire wolves) 
10. Giant Ghoul  
11. Green Dragon Ghouls (greedy scaly toxic breath ghouls) 
12. Dwarf Orc
13. Hobgoblin Wolfs (weapon using bipedal wolfs) 
14. Dwarf Small Roc (mounts for the dwarf elves or orcs)   
15. Giant Giant Spider Crab 
16. Giant Giant killer bee (they are getting quite big!)
17. Brigands giant killer bees (killer bees who ambush people to hoard their stuff) 
18. Unicorn giant killer bees (white bees who produce magical honey for maidens) 
19. Dire Island Wolves (cosmetic variant Dire wolf) 
20. Climbing Wolves